Diatomaceae (siliceous algae)

by Friedrich Hustedt

Original title: Kieselalgen (Diatomeen)

From: Sammlung: Einführung Kleinlebèwelt' (SerieS:; . Introduction tb the world.ofjnicrci-organisms), 1-7(),. 1965

Translated by the Translation Bureau(ËS) Multilingual Services Division' Department of the Secretary of State of Canada

Department of the Environment Fisheries Research Board of Canada Great Lakes Biolimnology Laboratory Burlington, Ont. 1973

114 pages typescript DIATOMACEAE





AUTHOR - AUTEUR Friedrich Hustedt

TITLE IN ENGLISH - TITRE ANGLAIS Diatomaceae (siliceous algae)



Sammlung: EinfUhrung in die Kleinlebewelt

REFERENCE IN ENGLISH - REFERENCE EN ANGLAIS Series: Introduction to the world of micr6-organisms








Eia.vironn^ent ^^c . 51.ip. viv., Lib.., i r.l. I"I zl.d Waters t3URE`kU NO. . IIANGUA G E TRANSLA•TOR 1 I NI T1 A LS ) I^0'[SU OUREAU LANGUE TRADUCTEUR ' (INlT1ALES)


Reference: F:iustedt, Friedrich; KieselaÎgen (Diatomeen). Stuttgart: FrancTd:i'sche Verlagshandlung W. Keller & Go., 3rd edition 1965.

Diatomaceae (siliceous algae)

Dr. Friedrich Hustedt Bremen (Germany)

With 35 drawings throughout text and 97 illustrations on 4 Plates

(Contents Page No. 0 @rig. Transl. Odhat are "'s^t liceou^s a Igae'Y? ...... 7 2 General structure of the diatom cell ...... 8 4 Structure of the cell wall ...... 13 15 Raphe and motility ...... 19 25 GeTl contents ...... 2.3 34 Formation of colonies ...... 24 36 Reproduction ...... 27 41 Variability ...... 33 52 Liâcology ...... 34 54 a) Hydrogen-ion concentration ...... 34 55 b) Calcium content ...... 35 57 c) Salinity ...... 36 58 d) Nitrogen and phosphorus ...... 36 60 e) Other chemical factors ...... 37 61 f) Water current ...... 37 61 g) TemperRture ...... 37 62 w h) Light ...... 39 65Z Ln ^'lotation aids ...... 39 65h Nutrition and 67 <1 ^ ^ F- prLp^>.ration of cultures, ...... 40 ^ Collection of material ...... 42 70cn c :x ^ 727 ° O cu Inspection ...... 43 - Preparation of raw material ...... 44 74cs ` ^ 0 Mounting and conservation ...... 45 78 Drawings and photographs ...... 47 81 0 1^ 4 (a The importance of the Diatomaceae...... • 48 83^' Tables for determining familles and genera ...... 49 84 References ...... 62 Inc: ;^: ^ Legends of plates :i-IV ...... 64 108 ^-- Index ...... 69

aOS-zoo-I O'31 2.

What are "siliceous algae" ? p. 7

The answer to this question lies already in its formulation. They

simply are algae with silicified cell walls. For about one and a half

century many investigators and lovers of nature have devoted themselves

to the study of these unique organisms which were regarded by some to be

of and by others to be of vegetable nature. These early investiga-

tors were first intrigued by the multitude of such organisms in our waters

and the capacity of independent movement, unknown in the vegetable kingdom,

but observed_in some species; later, with the perfection of the microscope,

they were fascinated by the structure of the cell walls which reveals the

artistry and creative power of Nature in extraordinary abundanceand by which alone the living plasma is rendered viable. Soon enough,the com-

plete rigidity of these cells in contrast to other plant cells,,=and their

resistance to chemical reagent's was observed and it.was realized that the

cell wall consists of a siliceous membrane embellished by multifaceted

"adornments." On account of these siliceous walls, they were called "si-

liceous infusoria," "siliceous Bacillaria," and,._finally, "siliceous al-

gae." In contrast to this characteristic- German designation, the custom- ary scientific terms "Bacillariophyceae" and "Diatomaceae" give no clue as to their nature. The name"Baciliariophyceaé1 relates to the rod-shaped frustules of the first-known Bacillaria, while the most widely-used

terml'Diatomaceae"has been derived from the genus Diatoma and is indicative merely of reproduction by cell division,which is known, however, to be

the most common process in the world of organisms.

The silicification of the cell walls led to a wealth of differen-

tilations from other organisms to assure viability and reproductivity; hence, 3.

the Diatomaceae form a rather isolated group within the vegetable king-

dom although, here and there, a faint resemblance^reminiscent ofa clo- 0 ser relationship,exists.They belong to the microscopic unicellular orga- nisms which play a prominent role in the economy of our oceans and in-

land waters. In numerous sediments their nearly indestructible valves

bear witness (in some cases after millions of years) to growth and decay

on our planet, the elevation and submergence of its land masses, and

the eternal battle between the sea and the land. The most minute frust-

ules measure 0.0025 mm, while the largest discoid valves measure close

to 2 mm,and rod-shaped species may surpass the length of 2 mm; however,

such "giants" are rare exceptions.

The environment of all Diatomaceae is the water, whereby, for some

species, the most minute amounts of moisture.will .suffice.

patches-on tree trunks, glass panes in greenhouses, the atmospheric moist-

ure settling on mountain walls, and the damp soil,all accommodate more or

less dense colonies of aerobic ("air-loving") diatoms, frequently of ex-

tremely delicate structure. In our waters they populate not only the open

water as floating plantswith the help of special processes, but cover also

the bottom as far as light can effectively penetrate, and all substrates

along the shore zone such as higher plants, wood and rocks. There, usu-

•-ally-fiogether with other algae, they.frequently form a thick brownish car-

pet in which numerous minute animalcules find food and shelter. Some spe-

cies,especially of the genus Nitzschiaaoccupy even highly polluted waters

where they provide,together with bacteria and several other organisms,the

preliminary conditions essential for the biological self-purification of

these waters. 4.

Industry also has taken hold of the diatoms and produces dynamite, insulating material for heating systems, and filters from the fossil depo- sits known as diatomaceous earth or diatomite.* Emperor Justinian* alleged- ly used,as early as 526 A.D., the "light, floating bricks" -- again diatoma- ceous earth -- in the construction of the St.Sophia cathedral*.

General structure of the diatom cell

In the literature, the diatom cell is usually called "frustule"

(from the Latin frustulum = small piece), or, even better, "theca" (Greek word, meaning box, capsule) since it is indeed constructed like a pillbox of two main parts, namely the lower bottom * part or "hypotheca" and the overlapping cover or "epitheca" (Fig. la). But just as the two halves of a pillbox usually again consist of two separate parts, namely bottom and top each with its connective part, so also are the epi- and hypotheca of the diatom frustule each composed of two distinct parts. Cover and bottom are called shells or valves, the connection is formed by the two zones capable of movement over each other and known also as pleurae. However, in most cases the edges of the valves are more or less inverted and par- ticipate,thus,in forming the suture. This portion of the valve,which is very conspicuously developed, for example,in the genus Meloseira,is known as the connective zone. Thus, the mature frustule of a vegetative diatom

*) Translator's notes: Diatomite serves to filter and clarify many liquids. It is -an excellent insulating material for boilers, blast furnaces and refrigerators. It is used also as a mild abrasive in metal polishes, scouring powders and tooth pastes. (M.H.Berry: The Algae; The Book of Popular Science, 4:294 (1958), New York - Toronto, The Grolier Society Inc. Justinian I. (Flavius Anicius Justinianus) A.D. 483-565, Roman emperor. Properly: Hagia_Sophia, a -church in Istanbul (Constantinople) re- garded as one of the wonders of the world. Jus tian entrusted its design and construction to two distinguished architects, Anthemius of Tralles and isidorus of Miletus. 5. E consists at least of the following parts (Fig. la): Cover (upper or epi- valve), upper (= outer) connective zone (epipleura); lower (= inner) con-

nective zone (hypopleura), bottom (lower or hypovalve). These parts are

not inextricably intergrown with one anothErbut can easily be detached me- Il chanically; this fact is of decisive importance for the frustule's viabili- 0 ty and for reproduction. Since the two bands that form the suture are not immovably united, it follows that the two parts of the frustule, namely

epi- and hypovalve, are capable of movement over one another just like the

two parts of a pillbox. For this very reason, the guideway controlling this

direction of motion and, hence, connecting the morphological centers of both 0 valves, is called "pervalvar axis" (Fig. lb). Of course, it runs also through the morphological center of the frustule constituting at the same time its

longitudinal axis,although, in most cases, it does.not represent the longest

extent of the frustule. Axes intersecting the center of the pervalvar axis

at right angles are called "transverssl axes;" the plane determined by them

is the central cross-section of the frustule. If the latter is circular,

the transverse axes are alike and may,thereforetsimply be.considered as the

diameter of the frustule. However, if the cross-section is more extensive

in one direction, that is, if the valves have an elliptical to linear shape,

Fig.l: Basic structure. P a = apical view; b=.axes and planes. V= valves, P = connective zones, ,r E epivalve, H = hypovalve, A-B = per- F valvar axis, C-D = apical axis,E-F = r o o transapical axis, G-K = parapical axis, L-T1 = paratransapical axis, C-E-D-F = b valvar plane, G-H-J-K = apical plane, L-M-N-O = transapical plane. 6.

the two main axes of the cross section each require a snecific designa- tion since orientation throughout the frustule would otherwise be impos- sible. The longer of the transverse axes is,therefore,designated as api- cal axis, and accordingly, the shorter one as transapical axis. These lines determine the principal planes of the frustule, they are essential systematic factors; an intelligent comprehension of the microscopic pic- p.9 ture would be inconceivable without them. The-aforementioned central cross-section determined by the transverse axes, that is, the apical and the transapical axes, represents the valvar plane, so designated because

it runs parallel with the valves and, hencé, duplicates in most cases the

form of the latter. The plane determined by the pervalvar and apical axes

is called apical plane, that determined by the pervalvar and transapical

axes is termed transapical plane. All axes mentioned.relate.always to the

cell body; hence, their course runs through the frustule. However, in

some instances, it it necessary to name also the corresponding axes of

the valves; however, the misleading terms "longitudinal" and "lateral"

axes are to be avoided since the longitudinal axis of the frustule is not

identical with that of the valves. In fact, the latter runs parallel

with the apical axis and is,therefore,called parapical axis, while the

lateral axis of the valve, running parallel with the transapical axis,

is designated as paratransapical axis. Besides the nomenclature here

applied and-originally introduced by Otto MULLER, other terms have been

suggested,but these are, -on purpose, not mentioned here since the appli-

cation of different terminologies for one and the same topic can only

lead to confusion. MÜLLER's terminology, once thought through and tried

out in practice, is most simple and clear without ver leading to mis-


Ufidêrctândings. The main sections do not necessarily-have always

absolutely straight; depending upon the shape of the frustule, they may.

frequently be arched or bent in one or both directions, often S-shaped,

and not seldom also spiraling around one of the axes. Furthermore, both along the frustule,when separated , one of the principal sections, halves of /‘ may be either similar or different. In the case of similarity, their corn-

on axis shows isopolarity, in the opposite case heteropolarity (Fig. 2).

Here again, it must be kept in mind that axial polarity always relates to

the cell body, and that structural differences of otherwise similar valves

are not taken into account; in doubtful cases, both aspects of the frus- tule should be inspected, namely the valve view as well as the zone view (if seen in zone view, frustules, split open on one end,may simulate hete-

ropolarity!). As we .have seen, the epivalve overlaps the hypovalve and

IS therefore always larger, in thick-walled species even considerably so.

nence, the pervalvar axis would, strictly speaking, always represent he-

teropolarity and there would be no way to distinguish between the spe-

cies which,.according to their form, show true heteropolarity) and all the

rest. FOr this reason, if it is only a question of difference between

the sizes of epi- and hypovalves, we accept the pervalvar axis as being

isopolar '(but not if such differences involve the poles of the two re-

maining axes!).

Fig.2: Polarity of the axes. a I . (isopolarity), c 2 pervalvar axis (heteropolarity); el (isopolarity), axis (heteropolarity); .... h (isoporarity), apical axi (heteropolarity). LJ


the As for Asimilarity of the cell halves on either side of the princi-

pal section, Otto MULLER distinguished complete similarity from resem-

blance, symmetry from consimilarity. This differentiation is, in my opin-

ion, unnecessary; we can dispense with emphasizing consimilarity because,

here again, it is merely a matter of difference in the sizes of the two

valves, which is of no practical importance for the understanding of the

frustule's morphology. On the other hand, in agreement with MÜLLER, I dis- p•10 0 tinguish the following four types of symmetry which are of . decisive impor- tance also in systematics:

0 1. Mirror-image symmetry (one,Yalve of the frustule being the

mirror image of the other);

2. Diagonal symmetry (oneVâlve of the frustule being turned ri against the other by 1800); 3. Antisymmetry (the mirror image of one Valve of the frustule

0 being turned against the other by 1800);

4. Asymmetry.

Fig_3: Mirror-image symmetry. Eunotia djdyma; valvar form and po- ]sition of raphe in b (hypovalve) re- ^present the mirror image of a(epi- 0 ;valve).

. Fig.4: Diagonal symmetry. Pinnularia flamma; the course of the raphe on one valve is the opposite"of that on the other.

Fil 9. 0 MÜLLER's theories are not in all cases easily applicable to actual conditions in the Diatomaceae. Therefore, a practical method is offered 0 here which makes it easy to understand the conditions of symmetry. For each of the first three examples we need a piece of white carton (approxi-

mately postcard size) and a piece of tracing paper; the sides of the car- I ton are to be numbered 1 and 2, the sides of the tracing paper 3 and 4. Examplé l(Fig.3, p.8): An entire frustule of the largest avail- 0 able species of the genus Eunotia (valve view) is selected as the object. With the help of.a drawing pen, a sketch is made on side 1 of the carton

0 illustrating the valve as it represents itself to the observer, that is, 0 its outline and branching of the raphe only. In the same manner, a sketch of the other valve of the frustule is made on side 3 of the tracing paper. 0 However, since this second valve is seen from its inside, the sketch is traced with India ink onto side 4; both pieces (sides 2 and 3) are then 0 pasted together in such a fashion that the sketches perfectly match. If 0 side 1 of the drawing is now held up against a plane mirror, its image will be identical with the sketch on side 4; hence, the two cell halves

show mirror-image symmetry.

Example 2 (Fig.4, p.8): A large Pinnularia species whose terminal

0 fissures on either side take opposite directions serves as the object.

Following the same procedure as described for example 1, we find upon e viewing the image in the mirror that it does not correspond to the out-

lines on side 4; to achieve this, the drawing held against the mirror

must be turned by 1800 about its parapical axis, and hence, the two the valves are subject to diagonal symmetry (apparently, turning,mirror and,

N 10.

thus, the imagee leads to the same result, but in this manner the inside

of one valve appears as its outside and this creates a false impression; the

correct image can be obtained only by turning the original).

Example 3 (Fig.5): Sketches of Nitzschia sigma valves or another

large sigmoid Nitzschia species are prepared in the same manner as before.

Uhile the mirror image matches in its outline the sketch on side 4,

the conceiled raphes(indicated by the keel puncta) are located on opposite

sides. In order to match their position also, it is necessary to turn the

- mirror image (!) by 1800 about the pervalvar axis; hence,the two halves

are antisymmetrical.

1■1111111•1101MIIIMMIM MOM%

Fig.5: Antisymmetry. Nitzschia sigma, outlines of >valves show mirror-image symmetry, but raphes are on opposite sides; turning a by 180° about its axis results in b as mir- ror image.

Fig.6: Torsion'phenomena. a = Surirella spiralis; b, c = Cerataulus turgidus:

However, in the case of antisymmetry, matching pictures can be ob- p.11

tained also by turning lem one valve (not its mirror image) by 1800 about

its pervalvar axis, since, in this manner, the internal and external views il,

are not switehed a-rou:nd, and there€ore, OLLER's l.nterpretations regar-

ding diagona). synunetr.y ond antisynmet.ry cari be replseed by a simpler epm-

mon formula. Bach pa3-r of frustule halvs,divided by gne seetipn,always

has one axis in common 3ahile the two remaining axes either fnaiçe a parallel f pair or run transversaily to otie another, Thus, the Pervalyar aKis is and El common to halves that are divided by the var plane,^ the transapieal axis to those divi.ded by the apical plsne, ilenee, eases ether than mi.r_ 0 ror-image symmetry may be summarized as foiiows; When deaiing with dia- gonal symmetry, one hali: of the frustule is turned by i80° about one of

the axes that are not eommon to both halves, while, in the ease of 4rit3-

symmetry, one hal-f is turned about the axis eo^unon to both liaives; anti-

symmetry is a eopnlii^a-ion of ^nirrOr=iinage and diagonal syr^Metry,

Examole 4 (Fig.2, p.7); Asymmetry 9pp13-es to all frustules whose

halves have a heteropolar axis in eomnion,

The afore?ner^tioned t^^es represent only the main gFoups, but they

are of guidance also in understanding thep intermediate forms ^akiçh are due

to torsional jnanifestations (Fig.6, p.10). All conditions of sym-

metry relate,of çourse,strictly to one plane only so that a frustule may

simultaneously feature different types of syc^metry (Fig.3, p.8t Eunotia,

mirror-image symmetry in relation to valvar and transapiçal planes, but a-

symmetr-y-in relation to apical plane).

In addition to the valves and the çonnective zone, still other

structural components of the cell wall exist in many Diatomaceae)whiçh

also participate in the enlargement of the frustule in longitudinal direc-

tion. They are inserted between valve and çonaective zone ând are, there-

fore, referred to as inte.rstit3al bauds or "sopulae" (F3g,7, p.12__). Their

Translator's note: In some Fnglish publicat^flAS -also referred. to --..._. .._. - _--- ^---- as l'eonneçting bands. " - 12.

of the valve, but they LI outlines follow of course in most cases the form are not intergrown Tiiith the valve or the zone; instead, the bands are

conneèted to these and other .parts of the frUstule only by folds, forti- o fied ridges, or closely adjacent bladelike edges. The number of bands varies greatly in different species. Some diatoms are consistent, in for-

ming only one connecting band for each half of the frustule, while other n . species feature many such structural parts. Their form is equally vari- able; it is about circular if the bands are extended over the entire ra-

dius of the -frustule while, in other cases, it may consist of several rows p.1

of imbricated scales arranged in pervalvar direction. Circular bands are,

as a rule, open at one end; in the case of several bands, open and closed

ends alternate so as to prevent bursting of the frustule when internal pres-

sure is growing strong. n . Fig.7: Interstitial bands. a = circular (Rhizosolenia); b = scalelike (Rhizosolenia);

. c-k = with septae (c-e Tabel- laria, f-h Tetracyclus, i,k Mastogloia).

IMI. ...Tel

Fig.8: Grammatophora with undulate septae. 0 13.

In numerous diatoms, the ringlike bands extend special partitions

X more or less deeply into the inner cell which run usually parallel with the 0 surface of the valve, or form, in other instances, a narrow band of small compartments usually extending from one end of the frustule to the other,

but sometimes confined to the central part of the valve's margin. These

partitions,originating from the bands, are called "septa" (Fig.7, p.12);

their form varies from straight to undulate (Fig.8, p.12), and they some- 0 times,a hooklike curve; in most cases the septa start only from one (the closed) end of the connecting band, but sometimes they penetrate

the entire frustule and are then more or less perforated to avoid obstructing

the connection between the plasmatic cell contents. They grow before or

even during silicification,starting at the connecting bands, and from the

outside inwards. Whenever parts of the septa meet in the center, more

or less pronounced diaphragms are formed. In certain species the ends of u the valves show similar formations, e.g., at the poles in some species of the genus Stauroneis (Fig. 9). I call these structures "pseudosepta" *

so as to distinguish them from the true septa which are of greater im-

portance in'systematics and are direct extensions of the interstitial bands. k

Fig. 9 p. 13 r, Pseudosepta * at the ends of the valves in Stauroneis. ^'}

Fig. 10: ^., a Meloseir'&`dickiei with inner valves; b craticular plate of Navicula cuspidata.

:1 h ',7t'

Translator's note: Called "diaphragms" in pertinent English publications. The author, throughout his book, writes "Melosira"; -however, this c;enus should be spelled ' e oseira" 14.

Unfavorable environmental conditions, e.g.,-desiccation of the

habitat, leads in some species increasingly fi.o.:,the formation of internal

valves due to incomplete cell division;•-theÿ arè,.therefore, reminiscent

of the resting spores in other species. The best-known example exists in

Aieloseira dickiei (usually inhabiting moist mountain rocks and roofs) in

whicli a varying number of internal valves, stàcked like ice-cream cones, .^ , can, then, be observed (Fig.10a, p.13), while individuals living in water-

rich surroundings do not show any such formation. Of an entirely differ-

ent nature are the peculiar siliceous scaffoldings which grow as an inner

stratum parallel with the valves they are frequently found among forms of

Navicula cuspidata, and known as craticular plates (Fig.10b, p.13). Some

investigators believe that their formation is due also to changes in the J concentration of the surrounding medium. It is possible that they are in- duced by environmental changes, but here, the result differs considerably

0 from the internal valves, and the craticular plates are often enough ob-

served in specimens from areas where environmental changes have not taken

place. However, most striking is,the fact that division of a cell featur-

ing such craticular plates results in a completely new form which is fully

developed and, hence, viable,but entirely.different in the-arrangement.oF

the structural elements from the mother frustule; viewed separately and

without knowledge of the craticular plate phenomenon, the new frustule

could doubtless be mistaken for a separate species. By contrast, the in-

ternal valves are incapable of forming separate viable frustules; instead,

they undergo reduction within the-frustule as their number increases.. Frus-

tules resulting from craticular plates are. - according to my observations -

highly suggestive of mutation, and the biological role of craticular plates 15.

is, in my opinion, hardly comparable to that of the internal valves.

The cell contents consist of plasmatic components which will be

discussed in detail later (p. 34).

Structure of the cell wall

The cell wall of the Diatomaceae consists--in addition to the

siliceous membrane which is probably made up of an opaline silicen com-

pound--also of a pectinous coating. MANGIN assumed that the pectinous

substance were.intimately combined with the silicon compound, and this

despite the fact that he successfully separated it in the form of a pee-

tinous membrane from the silicic acid part: However, LIEBISCH, a former

student of G. KARSTEN, proved about three decades ago that the pectinous

substance forms an independent membrane on the inside of the siliceous

wall to which it is closely fitted. Upon removal of the siliceous stratum

with hydrofluoric acid, its structure is still recognizable on the resi-

dual pectinous membrane and it is, therefore, possible that the latter

projects also into the vacant spaces and pores as far as these are ac-

cessible from the inside. The existence of the pectinous membrane is of

considerable importance to the Diatomaceae, and helps us to understand

many of the otherwise inexplicable, or fallaciously interpreted, phenome-

na such as the extravasation of plasma from thQ mothe.r frustutes during

auxospore development, or the absolute cohesion of individu41 frustule

components despie their noncoalescence and Lhe ofte-u QI.I.HWral.2te inter- ri nal pressure. But it also renders obsolete the theory of tne ulax.ipill and minimum sizes of pores which had been develQped before dlsçovçry of the

pectinous membrane and advocated chiefly by 9tto dLLER.

Upon sufficiently high magnification almost 4“ si1Lc.eou membanes

of the Diatomaceae show some markings and it is questionable w.4.Lber trti 16. ly homogenous membranes really exist. Since the valves are not stained, so that there is no chance that the structural images could be created by the various hues, the markings must be attributed to the alternate suc- cession of dense and less dense, or completely perforated,membrane sec- tions. The denser parts absorb more light than structures of lesser den- sity and they appear, therefore, dark under the microscope when the sur- face is turned toward the observer ("high focus"), whereas less dense structures, having greater translucency, are shining up brightly under high focus. Upon viewing the lower-situated inner surface ("low focus"), the situation is reversed: Denser parts aPpear bright because light is retained, while structures of lesser density appear dark. As a "rule of thumb‘," this optical reaction must be taken into consideration in all structural examinations since it permits - a comprehensive analysis of the microscopic picture. However, it is an important requirement that a sing- ly refracting medium is employed for such examinations (most substances commonly used for mounting meet this requirement; the newer synthetic products are always to be tested beforehand as to their optical proper- ties!),-since birefringent resinous media would of course reverse these effects. Furthermore, to avoid misunderstandings it must be emphasized that, when we speak of "dense" and "less dense" membrane structures, these terms are not to be confused with "thick" or "thinner" since the "thick- ness" of the frustule wall has nothing whatsoever to do with it. Dense areas may sometimes be thinner than adjacent areas of lesser density be- cause they contain cavities. Therefore, the term "dense" implies "mass. density" of which there is less at hollow parts of the wail than where the membrane forms the partitions that divide the cavities. The optical manifestations just described lead us now to the following fundamental - 17.

concept: The structure of diatom membranes is,foremost^a consequence

(or "function") of differentiation of the mass-denGity throughout the

frustule wall.

The denser parts of the wall - at least those of the valves -

seldom develop into areas but are, as a rule, seen as narrow, bandlike

markings forming straight or irregular, very often zigzagging, striae;

frequently, they are very narrow and appear then in the microscopic pic- F-1 ture as "lines". However, regardless of their width, I shall refer to.

them uniformly as "costae." Membrane parts of lesser density show great

variation not only in their form which depends upon the arrangement of

the costae, but also in their finer structure with which the following a in form pages shall deal at leastA of a basic outline. Already for nearly a cen-

tury have scientists labored to analyze their microscopic findings and to

construe from them the true structure of the frustule wall. Most of the

investigations were limited to the fine markings of Diatomaceae which made conducted ideal test objects, but these were usually •, , for the sole purpose of

testing one or the other lense system for its resolving power. Particu-

larly detailed discussions ensued concerning the structure of Pleurosigma

angulatum and many a word was written for or against one or the other con-

cept until Ernst ABBE, the famous mathematician of the Carl-Zeiss-Company*,

finally pointed out that all arguments were fruitless because of the phe- W nomena of diffraction which were not yet analyzable and interfered when-

ever the minuteness of the structure exceeded certain limits. During the

last three decades of the past century it was primarily Otto MÜLLER who, p. 15 n with exact methods (as far as this was possible with a compound microscope),

elucidated the structure of the frustule wall of a number of Diatomaceae,

mostly of the more robust species. Since then, only the author of the

*) Translator's note: In Jena, Germany, at that time. 18.

present publication has offered substantial contributions to this aspect,

which were also based on methodically conducted investigations. With the

construction of the electron microscope this work has entered into a new

phase, and during recent years numerous papers have been published featuring

equally numerous, sometimes more or less good, but often excellent photo-

graphs of Diatomaceae obtained with the ultramicroscope. However, although

with its help further advances have become possible in-the knowledge of

the finer structures of frustule walls, it must be said that the results

obtained with compound those men_who seriously studied the

subject,have, in essence,.â.lmost exclusively'been confirmed. The results

obtained with compound microscopes,as well as the electron-microscopic

photographs,reveal yet another basic fact concerning the construction of

the frustule wall: Every structured siliceous membrane of a diatom con-

sists of a network of siliceous costae forming intricate ramifications of

pores, puncta, and cells. The depth of focus of the ultramicroscope is 0 an undesirable feature in this kind of work since it makes it impossible to analyze thicker objects (which the siliceous membranes represent) on nt the basis of a series of horizontal sections which alone could give us an idea of their physical aspects. Furthermore, even the electron micro-

^ scope does not eliminate diffraction so that, with certain structures, w we have to expect interference patterns. Hence, photographic illustra-

T. tions present not only all aspects of the frustule wall.from the inner

to the outer stratum, but possible interference patterns may also enter

the same field and will,of course,show up in such photographs also when

viewed stereoscopically. Whether they will then be distinguishable from

true structures cannot, offhand, be taken for granted in all cases, and many a 0 19. picture of membrane structures obtained in this manner may hardly corre- spond to reality. Many microscopists will also have occasion tà. study electron-microscopic photographs, and I have > therefore,deemed it neces- sary to point to such possible errors.

Since the ultramicroscope has furnished proof that the structural elements -- as far as they lent themselves to examination -- which appear under the compound microscope as "puncta" or "areoles" are closed at least on one side by pellicles, the question arises whether true perfora- tion really does exist in the valves of Diatomaceae. The answer has to be confirmative, because true perforations are: 1. The raphe (to be dealt with in detail in the next chapter, p.25), 2. the "mucousnor "gelatinous pores", 3. the "interstitial mesh" seen in some of the Centricae, 4. the

"isolated dots" in the central area of many species among the Pennatae.

Fi.11: Gelatin pores. a = Stephanopyxis with hollow processes*; b,c = Eunotia, gelatin pores in the coleoderm; d = Synedra, porus near end of valve*; e = Tabellaria, porus near center of valve*.

*) Translator's notes: a = processes described as "crown of spines" serving concatenation, in Synopsis of North American Diatomaceae; d,e, "terminal" and "median pores", respecti\re- ly.

Gelatinous or mucous pores are found mainly in colony-forming species where they provide the material for the connecting substance, but they may occur also in other forms in which concatenation or sessile existence 20.

are unknown. Very extreme structures of such nature can be observed in

some marine genera, e.g., Stephanopyxis (Fig.11a, p.19), where they form

longer or shorter,extrafrustular, hollow processes which probably secrete

the agglutinant wich holds the processes of adjacent frustules together and, n. thus, conects them to chains. However, in most cases, the gelatinous po- res are minute,cone-shaped, pierced, projections into the inside of the

frustule, and have a fixed position in individual species. In the Centri- E . cae they are usually located close to the valvar margin but often also at about the center of the valve; in the Pennatae they are nearly always

I D seen close to the poles, either on one or On both ends. Very seldom are ge- latinous pores observed in the center of the valves in the Pennatae, un-

less the so-called "isolated dots" of many species (to be discussed below)

should also be considered as àelatinous pores Easily spotted are the gelat-

inous pores in the larger species of the genus Synedra which, as a rule,

feature one porus in the valve close to one pole (Fig.11d, p.19). Less

easily recognizable is the porus in the Eunotia species because, here, it

is usùally embedded in the plication of the valvar pole, and hence, it

becomes visible only under low focus (Fig.11 b, c, p.19).

17.3WP2ert›-: Fia 12.• "Interstitial mesh" in Coscinodiscus perforatus'\ 6 ÎM n. 1,r • • k,r1•,'"% . e,•I'hi,•!.:P

•■••■•••••■• The "interstitial mesh" consists of minute "dots", which are more or

less numerous in some Centricae with areolate valves; they can definitely N not be considered as areolation products, that is,- as "remnants" missed by *) Translator's note: Called "cells" in pertinent Engl. publications. R 21. the areolation process, since they are constant in some species, and absent El in others with similar areolation. They are always situated singularly be- 0 fore the shorter radial rows of areoles, and are conspicious not just by their minuteness but also by their enhanced brightness, that is, by greater D translucency which is greatly indicative of membrane perforation. The pur- pose of the "interstitial mesh" is not known, but here too, we may be dea-

ling with gelatinous or mucous pores (Fig.12, p.20).

The term "isolated dots" has been applied,so far^in earlier descrip-

0 tions to structural elements in the central vicinity of the valves of navi- .

cular diatoms. These are sometimes situated close to the central nodule,

in other instances they may appear in front of the central structural columns 0 and give the impression of constituting scattered parts of the normal struc- ture. They are observed mainly in the genera Navicula, Cymbe.lla, Gomphonema,

0 and Gomphocymbella; their position and usually also their number are con- 0 stant in most species, only a few forms show slight fluctuations in their number. As far as I could examine these structures - which is the case in

{! almost all species in which they occur -- they were identifiable as orifices

of canaliculi. Their true nature is best visible if their course through

0 the valve has a slightly sloping angle since they are then seen in full LI length and the differentiation betwèen outer and inner orificès becomes quite apparent (Fig.25b, p.37). However, in many cases, the canaliculi

run vertically through the frustule wall and are then not always easily

recognized as such, particularly when their position is just in front of

other striate markings (Fig.13, p.22). However, here again, true canaliculi

always give their presence away by their greater translucency, that is, by

p.17 enhanced brightness; when in doubt, a greater number of individuals of 0 the same species will have to be compared to establish whether the case in question represents a constant feature or merely an incidental struc- 0 0 22.

tural anomaly. In some spéci;es,- the dériâliciili âré extremely delicate

and the position of the ori^fi:c-es 6t flïé déritrâl rifldtrle can often be

established only with the-he-1-g of liiglï-lÿ r-efrâctivie- mounting medià, so

that they were discovered ônl-X quite r'-"6d6ntlÿ in a numbér of-'species.

Since they are, as mentioned- a-bôve; i dôristânt feât-ure of the relevant

species, they constitute a 156sW di-stiftgüi-shing mark in the identification

of species. Their purpose âlsci réinérns dbscuré; but most probably we

are dealing here again with g-6l,dtinôüs ôr ffihéôus pores; however, the

question as to the time of th-ëïr âctivitÿ = whether during concatenation

or auxospore formation - fèmdins ünânswéréd: Vèrÿ conspicuous in this

respect is the position of t-lïé CânâlïÉÜli in sôüië species. While, as a

rule, both orifices lie at t13(f i-rI§idé ô€ the valvé; the inner orifice (e.g., 0 in Navicula lagerheimii) MAY fd-téin tltis-pôsi€iôn iahile the outer orifice is situated at the margin ôf tlïé valve Aéfé It lads over to thezone. filaments 0 This species forms du'rfng its végé€â€ivé existence and this fact may have something to do with thè pôsiEiôn ô€ €Iié cânalicular orifices. I 111sé1atéd dots" ÿmbella x b = G6mphonema c = KaYicula

a F.ig.14: Longitudinal sections through cells of Triceratium; à= cells open on inside and closed on outside, b = reversed. ^ ) q A= outside ^.( J= inside j K= cells

The actual structure of the frustule wall consists of the network

of--costae; the enclosed spaces cân be described as "cells" although, in many 23.

instances, they merely form slight indentations. In the literature they

are usually described as punctae, areoles, or dots, depending upon their

size and form. According to the electron-microscopic findings it is highly

unlikely that cells exist which are open on either side, toward the inside

of the wall as well as toward the outside; all alveolar cells will be

covered at least on one side by a membrane which has, however, a certain

porosity. The other side may be completely open, or may,as a consequence

of T-shaped thickening and broadening of the costae (Fig.14, p.22), show

correspondingly narrowed openings; furthermore, since the costae differ

in thickness, particularly the larger cells may be divided into smaller

ones, so that KOLBE prefers to distinguish four types of areolar cells:

1. Undivided open cells, 2. divided open cells, 3. undivided, partially

open cells, 4. divided, partially open cells (instead of "divided" and

"undivided" distinguishes KOLBE between cells of the 1st and 2nd order),

The position of the porous membrane and the open or partially open cell

partitions varies; in many species the cells are open toward the outside,

in others -- probably in most -- the openings are at the inside. Size,

form and distribution of these cells depend upon the course taken by the

costae; a few examples shall be discussed in greater detail:

a) One system of costae only, running in transapical direction; genus Pinnularia (Fig.16, p.26). The costae extend from the zone to the median line of the valve which runs in apical direction, and protrude more or less deeply in pervalvar direction inside the frustule so that groove-

like cells are formed whose outer cover has been established, electron- microscopically, as a porous pellicle (open cells of the fst order). In many species of this genus, the inner endings of the costae are broadened in T-shaped fashion so that the cells have only a fissurai opening toward p. 18 24.

the inside (partially open cells of the lst order); in valve view, the

openings appear as a more or less wide band,crossing the costae. Some spe-,,-.:

cies of other genera (Caloneis, Diploneis) feature not just one but several

openings to the inside.

b) Valves with two crosswise arranged systems of costae (Figs. 9,

p.13, and 13, p.22). Apparently, this is common to most Diatomaceae; it

results in the formation of "puncta" which usually show, upon sufficient shape. magnification, a polygonal to circular^ As far as is known, these puncta

also represent porous membranes. We are dealing here with the outer walls

of more or less deep cells on the inside of the valves which are again ei-

ther completely open or show only a narrow opening toward the inside (Di-


Fig.15: Pleurosigma with three crosswise arranged systems of costae.

c) Valves with three crosswise arranged systems, structural type

according to Pleurosigma (Fig.15). The minute cells have a polygonal (hexa-

0 gonal) shape and are closed on one side by a porous membrane, but it is

not yet decided whether on the inside or the outside. According to electron-

microscopic photographs, the opposite side has,allegedly,. fissuriform ope-

nings in apical direction; however, definite proof has not yet been ob-

tained whether we are dealing here with completely open cells or if

this impression is due merely to diffraction images.

d) Twin-rows of areoles between the costae. In addition to the r

25. jD strong costae there are formations of finer striae So that the interstices

are dissolved into more or less delicate areoles-. They may occur in valves

having a single (transapical or radial) system as well as in those having

multiple systems of costae, and result in open or partially open cells of

the 2nd order. Diploneis diplosticta (GRUN.) might be considered as one

of the best examples. The cells formed by two primary, strong systems of

costae are divided by delicate secondary striae into smaller areolar cells

which are with the contents of the frustule by way of common

D. - circular openings on the inside of the valve (partially open cells of the

2nd order).

e) Areolate structures of the Centricae (Fig.12, p.20). As a rule, E there exist three systems of costae, one running radially, the other two taking a tangential to spiraling course so that polygonal areoles are for-

med which correspond to the outer and inner walls of polyhedral cells. A

porous membrane is formed either by the inner or the outer wall (either

case is possible!) while the opposite wall usually has a central circular

opening, in other words, it is partially open. Hence, radial rows of cells

are, strictly speaking, just "Pinnularia cells" subdivided by transversal

partitions into smaller cells; this division is manifest already in many

Pennatae without being indicative of any phylogenetic relationship.

Despite the considerable variability in the structure of Diatoma-

ceae valves, the structures can,most likely,in all cases be compared with

the types discussed; however, this requires an intelligent analysis of the

microscopic picture, based strictly on facts. [1 Raphe and motility The raphe, featured by only one group of Diatomaceae, is in its. ri original form a cleftlike division of the valve and must be considered 111 26.

strictly as an organ of locomotion. That it indeed serves exclusively

this purpose and has no part in metabolic functions is evidenced by the 0 reduction phenomena observed in those cases in which motion is abandoned in favor of sessile existence or concatenation. For example, in those

Cocconeis species that rest on a substrate, only the adherent valve pos-

sesses a raphe, while the unattached valve has lost its raphe. Similarly,

0 Navicula species changing to concatenation or sessile existence are known 0 to start losing their raphe completely or partially. The raphe remnants, frequently seen in unattached Cocconeis valves as well as in the Navicula 0 species mentioned,are proof that we are dealing here with true reductions. A shift of the raphe from the valve to the zone or the valvar margin (e.g.,

0 Eunotia) is due to similar causes.

0 Fig.16: Raphe of Pinnularia; a = valve view, b, d = ends of valve, c= center of valve, e = central nodule (slightly schematized). R raphe, Z = central nodule, Ek = terminal nodule, Ar = exterior channel of raphe, Jr = inner channel of raphe, P = terminal fissures, T = infundibulum, A z-- éxterior.median pores, Jzp = interior median pores, 0 Zr = open groove at central nodule, Zk.= channels at central nodule. 0

Fig.17: Frustulia Raphe with lateral project-L•ons at median pored and before terminal fissures. 0 27.

The progressive changes in structure and position of the raphe which evolved in the course of development have become of vital impor- tance in systematics. The two main types, the "Pinnularia raphe" and the

II concealed raphe," . have been described in detail mainly by 0. MULLER and

R. LAUTERBORN; additional investigations, particularly those concerned with the phylogenetic development, were in essence initiated by the author of the present publication. Apart from keeled and alate raphes is the Pinnularia raphe (Fig.16, p.26) the most progressive stage of develop- ment of this organ so that it seems appropriate to base our discussion on this form. Large individuals of PinnulAria viridis (NITZSCH) EHRENB. occurring nearly everywhere or any other large species of this genus may serve as illustrative object. Along the median line of the valve we see a more or less composite and twisted, centrally interrupted, system of lines. It is surrounded by a blank longitudinal field called the "axial area" which widens in the middle to form the central area. The lines define the cleft which divides the valve and is known as raphe. How- ever, the plane of cleavage shows interruptions and windings, the edges of the two valvar halves are interlocked by folds so that the single cleft is divided into the so-called exterior channel and the inner channel which open to the outside and inside respectively. Examination of the frustule in zone view shows that the aforementioned central interruption consists of a thickening of the mèmbrane extending as a cone inward, and designa-

ted as "central nodule." Both branches of the raphe terminate in the cen-

tral nodule with a tubular widening, the "central-nodular channels," the orifices of which are distinguishable, in valve view, as 'exterior and

interior median pores. An open groove, embracing the central nodule in a

semicircle, the "central-nodular groove", connects both branches of the 0 0 28.

raphe. Nodular structures are visible also on either end of the valve,

especially in zone view; these are the terminal nodules which,.in are contrast to the central nodule „ hollow. The exterior channel of the il raphe runs through the outer wall of the terminal nodule whereby the

plane of cleavage, the "terminal fissure," describes more or less spi-

raling windings, usually bending in a wide curve; the inner channel of

the raphe enters the terminal nodule from the inside, ending abruptly in

a spoutlike infundibulum.

Similarly complicated raphe structures can be found in several

other biraphe-bearing diatoms, especially also of the genus IMastogloia.

However, even within this group, we find conditions often much more simp-

lified whereby individual parts are distinguishable only with great diffi-

culty. The plane of cleavage is seldom interrup'ted,_the exterior and

inner channels of the raphe are superimposed .(threadlike raphe), or the

raphe enters the valve in an oblique angle and appears,therefore, in valve as view more or less A broad area, the terminal fissures are often very minute

or are replaced by a simple porus, and.sometimes, slitlike.lateral pro-

jections are seen at the median pores (very seldom also before the terminal

fissures). All these factors play an important part in systematics and

deserve, therefore, special attention in all examinations (Fig.17, p.26).

It is equally important to consider the position of the median pores as

well as that of the terminal fissures which are located either in continued 0 direction of the channel of the raphe, or may take a turn in either the same or in opposite directions.

Since, in addition to the Diatomaceae possessing a raphe, many

species exist without this organ, we are faced with the question where to K look for the initial stage of this structure and in what form. This prob- 29.

lem presents itself particularly in the Rhaphidioidineae group which in-

cludes the genera Peronia, Amphicampa, Pseudohimantidium, Eunotia and

Actinella. All species belonging here are characterized by a very short

partial raphe at the ends of the valves in which nodule formation is sel-

dom observed or only poorly developed (Fig.18) so that it must be assumed

that the first raphe clefts developed from a porus which expanded towards

the center of the valve. A certain difficulty arose from the position

of the raphe, since, in the genera Eunotia and Actinella, the greater

part of the cleft is located in the zone, and, in most species, little of

it projects into the surface of the valve,.namely only at the terminal no-

dule; however, in some species, a prolongation of the external channel

beyond the nodule . may be observed either toward the dorsal margin of the valve or, retrogressively, parallel with the ventral margin of the valve.

Raphe beginnings in Eunotia (a-c) and Peronia (d); a, c, d = valve view, b = zone view.

Fig.19: Concealed raphe in Epithemia (a,e) and Denticula (b-d); P = openings on the inside of the channel wall, Rs = raphe fissure in the outer wall. ;

On the other hand, several years ago I found l in Brasilian watersj a number p.21 of species whose raphe in its entirety lies in the valvar surface. Since, 3e-1.

furthermore, in these species the apical axis is less autcuat,e, ',end the

median mm costa, which is ventrally displaced in other mums

here along the median line of the valve, these species -11,e.serlible jinn-any

respects the rapheless species,especially of the genus Eynedre,

there can be no doubt that we must look for the first beennings re#he

formation among these and the Peronia species. The shift cf the reldhe

to the connective zone must already be considered as the -beginning ad re-

duction; the latter is more or less completed in the genus Ameicampe .(the

scanty traces of a raphe remaining here cannot be considered as its nascent represents state, but , its moribund state). It may seem paradox that, within the 1% same genus to which the origin of raphe formation can be traced, the re-

duction of the newly-formed organ should also have already started, but

this phenomenon can be observed in other genera as well; Naviculm species

change into Achnanthes or Fragilaria species, and it is my opinion that

all diatoms with a monoraphe are reduced biraphe-bearing forms.

Considering the present complexity of the Pinnularia raphe, still

greater perfection of its structure is hardly conceivable; still, it has been but ,achieved, in a completely different manner: 1. By elevation of the entire A II raphe system above the valvar niveau, and 2. by a shift to the margin of II the valve, combined with a gradual, complete reconstruction. In the first case, the axial area of the valve has more or less been raised so that a the raphe is placed on a ridge; in the extreme phase, the branches of the raphe rest on wingswhich, bilaterally, far surpass the outlines of the

frustule,as seen in Tropidoneis (Plate IV, Fig.83, p.114) and, even more II pronounced, in Amphiprora (Plate IV, Figs.$7,68, p.1 14) . But this trend of development has,thus l reached its Otimeç stage; WQ shall therefore

examine the changes brought forth in the sçeorld way: Already among the

genus Cymbella (Fig.13a, p.22) wç ebsgrvç 4 shift Of thQ etructurally un. 31.

changed raphe toward the ventral margin of the valve: On the other hand,

a considerably more pronounced shift is found:ciin the genera Epithemia and 0 Denticula (Fig.19, p.29). Here, the raphe is located entirely or partly in the valvar margin, and in the related Rhopalodia species (Plate IV,

Figs.89,90, p..114) it is, furthermore, placed on a more or less strongly

developed keel. However, here, the shift is accompanied by pronounced

structural changes: The fissure of the raphe has widened and forms now

a tunnel whose outer wall is still the passway of the exterior channel,

and divided by it and the median pores, but the inner channel in the in- 0 terior wall has been resolved into a number of fairly large roundish openings divided by septa- and easily distinguishable in valve view. A

raphe of this structure is known as a "concealed raphe." Further progress

is achieved in the Nitzschieae in that the concealed raphe is placed on

a keel and thus raised above the valvar level. This keel is even more

pronounced in the Surirelleae where it forms conspicuous wings in some of

the species and these are not only (as in the Nitzschieae) limited to one

margin of the valve but continue all around the.valve, thus creating the

false impression that each valve has two raphes (Fig.22; p.32). However,

the examination of certain species furnished proof that we are dealing

merely with the two extended branches of a single raphe so that, in fact,

one raphe only exists on each valve; it follows that the Surirelleae also

belong to those biraphedes that cannot be classified as a separate sub-

order equal to the "Birhaphidineae." The septa dividing the interior p.22

openings of the concealed raphe in Nitzschia (Fig.20, p.32) are the "keel

puncta" which, upon pronounced alation as is the case amông Surirelleae,

become "windows" that divide the openings,then representing "alate channels." 32.

They terminate in the "alate marginal canaliculus" in whose outer wall

the former exterior channel of the raphe continues as a fissure (Fig.21).

Fig.20: Concealed raphe in Nitzschia a= excentric in Nitzschia heufleriana b,c = near median line in Nitzschia dissipata (b = slightly oblique valve view, c = zone view) Kp = keel puncta

Fig.21: Structure of concealed raphe in Surirella; a = transapical section of valve, b = wings on valvar plane, c = alate marginal canaliculus in highest, d in lowest focus, e = transapical sec- tion of wing through one of the alate 0 marginal canaliculi, F = wing, Rs = fissure of raphe, Rk marginal canalicu- lus, Fk = alate channels, Fr = window.

Fig.22: Concealed raphe all around the valve in Surirella; a = valve view, b= zone view

P, Of what importance to the Diatomaceae is, then, the peculiar de- velopment of the raphe system just described? As has been pointed out al- f ready at the beginning of this chapter (p.25), the raphe must be looked

upon as an organ of locomotion. Various explanations have been offered

for the motility of some Diatomaceae which is a singular phenomenon in the

world of organisms. Still the most convincing concept is the hypothesis u proposed by Otto MULLER because it explains all phenomena with ease. On

the basis of observations made on Pinnularia specimens in India-ink emul-

sion*, MÜLLER arrived at the conclusion that motion is,here,the result 0 *) Translator's note: A process known as "negative staining." 33.

streaming of friction between the plasma raphe,and A through the the surroun- ding medium. The path of the circulating plasma is predetermined by the

structure of the raphe, but the direction of movement is variable. The

plasma can, for example, enter the inner channel by way of the internal

median pores and, following its course, reach the exterior channel through

the hollow terminal nodule and the terminal fissure; from there,the pladma

returns in the direction of the central nodule and finally passes the

channels at the central nodule. However, the direction of flow may also

be the reverse, or it may suddenly change, and furthermore, the plasma may

change from one branch of the raphe to the other by way of the inner chan-

nel embracing the central nodule. The direction of flow may be the same

in both raphes of the frustule or it may be opposite, that is, the two di-

rections may cancel each other out. All these possibilities offer nume-

rous combinations, which can definitely explain the changing direction in

the movement of diatoms, their pivoting, turning and staggering. Less in-

tricately designed raphes permit only simpler movements which frequently

consist merely in a slow crawl, often in pendular movements. Diatoms po s.. p.23

sessing only a monoraphe and being attached with the raphe-bearing valve

to a substrate are capable of changing their position on the latter. The

effect of motion and, thus, of friction is further enhanced by the windings

of the raphe system and also by its elevation above the valvar niveau which )

more or less,exposes the raphe. Furthermore, in species with pronounced

wing formation, the path of the streaming plasma, rubbing against the

water) is considerably lengthened. The advantage of a concealed raphe lies ri presumably in the fact that entry of the plasma into the raphe system is not limited to the median and terminal nodules, but that it can enter prac-

tically anywhere through the many openings into which the inner channel of O 34.

the raphe has been resolved. Possessing a raphe, that is, the power to

move about, is vital to many diatoms, and especially for the sexual re-

production of species whose frustules lead a solitary existence, or for

the soil-inhabiting forms since it enables them to maintain their posi-

tion in the surface layer*.

Cell contents

The live diatom frustule contains - in addition to plasma, nucle-

us, cell sap, and assimilation products - as its most conspicuous com-

ponents,the brownish colored chromatophores whose green chlorophyl is ob-

scured by other coloring matter such as carotene, xanthophyll, and yellow-

ish-brown carotenoid pigments which are closely related to fucoxanthin,

the pigment of the brown algae. Form and position of the chromatophores

vary greatly (Fig.24, p.35), lacking constancy even within individual ge-

nera. Hence, while they are useful indicators for the classification of

some species (e.g., of the genus Chaetoceros), they are of no use as cha-

racteristic features in the organization of a natural system of classi-

fication for Diatomaceae. Their size varies from small granules (the

coccochromatophores) to large plates (the placochromatophores) with

smooth edges in many species, but more or less notched in others; in 0 still other cases the chromatophores are bandlike, often with several windings. The coccochromatophores, found mainly in the Centricae, are

usually scattered through the entire frustule but may change their po-

*) Addendum (original p.64): It is, therefore, understandable that in some diatoms reductions,even_. complete elimination,may occur if the mode of life of these species varies considerably from the form typical for this group.

^. ^ 35.

sition, particularly in plankton forms, according to light conditions.

In diatoms having thicker setae,they are present even in these structures.

Placochromatophores are found mainly in the Pennatae but are not limited

to this group. Usually one or two plates are situated on the wall of the upon zone, but often they enchroachAthe valvar margins with their inverted and )

then,as a rule,notched edges. An important fact is that, regardless of

the position of the plates, the raphe system remainsl in general,free;

whenever the :placochromatophores spread across the valve, the raphe is

kept free through crevices in the plates.

rj4,5;7.7à7;;. Fig.23: Contents of Pinnularia frustule. ' 1;::":11 K = nucleus, D = double rods, Pb = plasma bridge, Pf = plasma threads, 0 = oil drops, Ch = edge of chromatophore plate which lines the zone but is • \J.i 11 not included in this illustration since it would obstruct the view of the inside of the frustule. Ki

Fig.24: Forms of chromato- P phores; a = granules, b = straight- , lined plates, c = notched plates, d = shredded bands of chromato- phores.


In deep and more or less polluted waters, colorless diatoms have

been found which engage in saprophytic nutrition; their chromatophores

are markedly reduced and without color. The cell sap of Diatomaceae usu- _ ally does not contain any pigments. However, one species (Navicula ostre- p.24

aria) is known as "blue diatoms"; their cell sap carries a blue pigment

which causes an intensively blue coloration especially at the ends of

the frustule which are free of chromatophores. fl 36.

The colorless nucleus (Fig.23, p.35) is usually situated in the

central plasma near the center.of the frustule, seldom near its wall.

Form and size vary greatly, particularly large nuclei are found in some

species of the genera Coscinodiscus, Pinnularia and Surirella. Very often,

observation is rendered difficult by the chromatophores and, generally,

examination of the frustule is most favorable in zone view. Of the re-

maining contents of the diatom frustule we shall mention only the pyre-

noids which have become evident in many species. One or several of these

more or less sharply circumscribed, mostly lenticular or globular, highly

refractive plasmatic bodies are found in the chromatophores. In contrast

to the pyrenoids in other organisms, those found in diatoms do not con- n tain starch so that the latter cannot be considered as leucoplastides.

As a matter of fact, the only assimilation product found in diatoms is

the fatty oil deposited in the form of smaller and larger drops outside U the chromatophores,within the plasma,or even in the cell sap. Under cer- tain circumstances, oil production may be very substantial so that the

extraction of fat from Diatomaceae cultures on a large-scale basis,as

has been repeatedly attempted,does not at all seem without prospects.

Formation-of colonies

Although most diatoms lead an individual existence, the forma-

tion of colonies is quite common and some observations seem to indicate

that this mode of existence is still on the increase. It is observed

not only in plankton but also in substrate-inhabiting forms and even

among soil dwellers. There are great variations in the form of the co-

lonies and the manner in which the frustules concatenate (Fig.26, p.39).

:The,.bonding or enveloping agent is gelatin or a gelatinous substance [


released by gelatigenous pores. The concatenation of frustules can al-

so be achieved by denticulate junction (Fig.25) whereby shorter or lon-

ger teeth, inserted along the margins, interlock. Whether a cementitious

substance participates in this process cannot be taken for granted in all

instances. The most peculiar form of concatenation appears to be that

of several Pinnularia species which form tabular colonies with the help

of denticulate junctions; the valves of adjacent frustules are united at

one edge only, but remain moveable in a rotating fashion at the edges

thus connectedj so that the colony is capable of opening and closing its [7: chain like Venetian blinds. The loosely connected or tightly closed

chains of the Meloseira species widely distributed among plankton are

formed by denticulate junction, while the prismatic frustules of many

Pennatae are united in filaments often of extraordinary length; frequent-

ly, 2,000 frustules and more may be counted in a single Fragilaria fila- .

Among gelatinous connections we distinguish gelatinous stipes ment:

(Fig.33b, p.95) by which frustules are attached to a substrate, gela- ri tinous intercalations (Fig.26, p.39) as cementitious substance between

the frustules, and complete gelatinous enclosures. Gelatinous stipes

are often mere cushions on which the frustules rest either individually, LI in fan-shaped fascicles, or in clusters. Frequently, they also form long,

Fig.25: Navicula lagerheimii ri filament formation by denticulate junc- tion. a = partial view of colony, LI b = single frustule in valve view.

D usually branched stalks,thus creating an enchanting arborescent a_ppea_FazlSe

of the colonies as can be observed especially in the genus Liemophora (Fig.33b,

p.95)^ sometimes found to cover marine algae like a thick carpet,

colonies of this nature are found also among fresh-water Af the

0 genus Gomphonema. Gelatinous intercalations glue the frustules tgg.ethex^

either at the full length of the adjacent valve edges uniting tbe fn!stuies

in filaments as in Fragilaria, or they are limited in the form of G ions to the ends of the frustules. Radiately arranged cushi4ns betwgen adjacent ends lead, to the formation of star-shaped concatenations (Aste-

rionella, Thalassiothrix), but if the cushions are arranged between alter-

nate angles of the frustules, this results in zigzag chains (Diatoma, Tri-

ceratium, Biddulphia, Grammatophora, among others). In many cases, gela- 0 tinous stipes and intercalations occur simul.taneously,.e.g., in the gep^^ Achnanthes, in that filamentous colonies,adnate on a stipe,are attaehed 0 to a substrate. Quite unique are the concatenations observed in some ge- nera of the family of Nitzschieae among which Bacillaria paradoxa* is.a I well-known textbook example. The frustules of this species form tabular t colonies (Fig.27, p.39) by way of contact between their concealed raphes. As a result of the streaming of the plasma in the ra.phes,the f_r-ustules

slide over each other,so that, with the different directions of the stream

in the individual frustules, the colony can stretch apart in manifold ways. p. 26 On the other hand, little is known of the conditions prevailing in the 0 closely related genus Pseudonitzschin whose fçisiform frustules çoncate- nate only by way of "apicifixation", in that the onds of consecutive frus-

0 tules overlap at a short piece only, but remain fixed in this position.

*) Translator's note: Synonym for Nittsçhin paxillifer (0. F.hIÜLLER) Heib., Consp. Diat. 113•(1863), under which it is listed in Synopsis of North American Diatomaceae by Charles $, BOYI:R (Philadelphia, Ac_ademy of Natural Sciences, 1927).


Fig.26: Concatenations. a = Tabellaria with gelatinous intercalations, b,c = Meloseira chains, d = Fragilaria filament e,f = Asterionella star (f = valve view).



;•;11!.. '

Fig.27: Bacillaria paradoxa [Nitzschia paxillifeiJ concatenation and individual frustule.


eireM11111•111■111111111 M


•••;,e..,., , , -) ---,--., - - I-,' • - .) , „,,' •..- l‘•:::v. - ...•• - . ., - . ' / • 411..i'.. ,1 I -. . - ' •. :: ...:::':' •• Ï:.1 ' I I 1 '" 1 ■ ibiumiaimeriebberaiiarriMmail -.„ z,,•i ' - ttle (S.;-•:..e0:, • .;-,;,,, ,...) 0. i, i g,, ii ;t Fig.28: Gelatinous structures. el:,‘I' l' '1 -'',• ill: l Y ‘:: D i '•.,:•..çi.:'''.:",.1,-:.. - e ie ' ' ' eo «j ''' '' 4+ gelatinous ;.--iti, .;',.- - - -..f._ ‘''' . , reà.y, . ,..1. a-c = Thalassiosira, ■ 17 -,,,, . --,#(.4. ' 0,7.,,e-,. ..-1 w ..,, --- ..“;,...., -...... -,. : ,. : .i , tie,,,,, thalloid, .-_,.i . ..;-;, Cr.? ‘_ ''b4:2.1 t :','•":,I, \ tn::i:_ ., 11 1 ; :P.. d = Cyclotella in gelatinous tube, 14;:•*t ,.• W,ii , . ;.r. single thread) and • e sira (e, r Coscinosira (f, several thread5).

The colonies assume, thus, the appearance of long rods in echelon formation

which—with adequate streaming of the plasma in the numerous and,here,ex- •

posed rephes--- . -shoatu rigidly through the water like-an arrow. 40.

Complete gelatinous enclosures (Fig.28, p.39) are sometimes ob-

served also around solitary frustules; in these cases their main pùrpose D is to enhance floatability. As a colony-forming substance they provide amorphous or organized nests; the amorphous "gelatinous thalloids" host

numerous randomly arranged frustules (e.g., Cyclotella and Thalassiosira

species). The organized enclosures take the form of simple or ramified

tubes in which the frustules are arranged in single or several rows,

either one behind the other or side by side. Frustules possessing a ra-

phe are capable of moving about inside the tubes. In some cases this

leads to characteristic motions of entire tuftlike ramified tubes. fm-

bella prostata is the best-known tube-forming species among fresh water

diatoms, however; this growth type is far more frequent in our seacoast

areas. Species of the genera Navicula ^and Nitzschia occupyjin such co-

lonies,the higher algae and other substrates, and great numbers of the

facilely--floating tubular tufts of Amphipleura rutilans can be collected

along the marshes at low tide. Diatoms capable of independent movement

can leave the gelatinous nests, and it must be pointed out that, at any

rate, all colony-forming species can also live independently and, in some W cases, solitary frustules are seen more frequently than concatenations;

on the other hand, species usually leading a solitary existence may some- B! be times concatenate. This mayAdue essentially to nutritive conditions and

4 cell division in that, under favorable conditions at the height of pro- 0 duction, cell division takes less time than the daughter frustules need to p.27 separate:from congenital union. Furthermore, under certain circumstan- 0 ces depending upon time and locality, setae formation, normally unknown in these species,occursin certain plankton forms and leads also to the 41.

development of chains. This is the case, for example,in the widely dis-

tributed Stephanodiscus hantzschii, and only a few months ago I observed

this in the also widely distributed Cyclotella striata. Many decades ago,

LEMMERMANN described similar chains,which hitherto had been very seldomly

found) as Cyclotella chaetoceros because causative relations were still un-

known. Hence, this variability in appearance must be emphasized to avoid

errors in our investigations.


Reproduction and continuity of species is secured for all Diato- maceae through cell division and auxospore formation, in some groups„fur-

thermore) through microspores, resting spores, or both these forms. The most important form of reproduction is cell division; in some species,

divisions take place in such rapid succession that, with the onset of the

season of vegetation, the still nextto bare shore regions of our waters come suddenly -- almost "explosively" -- alive with countless billions of diatom frustules of a great variety of species. Since the silicified walls of the frustule do not allow additional growth, the cell division of the Diatomaceae differs from the division of other cells . and, as a re-

sult, future generations are subject to lawful consequences which must be

taken into consideration in all systematic investigations. More or less intentional neglect of these irrefutable facts is bound to lead to seri- ous mistakes in die classification of "variations" and the definition of


The first indication of the beginning of cell division is an en-

largement of the frustule in the onfy possible direction, namely that of

the pervalvar axis, whereby the two frustule halves glide apart without

being rendered completely ajar (Fig.29, p.42). To avoid the latter con- 42.

Fig.29: Wall of frustule ) , during cell division of Gram- 1 . . matophora; a = frustule at f frus- itretule ' b;i :epleal.rirtiZl inj : );I, and insertion of expansion 111 1 \ rings,just prior to division, . 111 i c =daughter frustule after di- il ! I . vision (septae_still missing i IL) iç!'il Illi in younger half ), d = begin- e c' ning of septa. formation.

dition, the connective zones of some species are extended by appositional

growth of expansion rings added to the girdle bands at the free

edges. Where a larger number of bands exists, new bands are inserted to

obtain the required size (length!). More or less simultaneously with the

gradual separation of the frustule halves, nuclear division begins which p. 28

-- not withstanding the manifold variations also among diatoms -- is es-

sentially similar to the mitotic nuclear division in higher organisms,

so that I shall refrain from going into details here. The daughter nuclei

move apart in the direction of the two valves and, in the case of coccochroma- these tophores, are distributed in the same manner to both halves of the frus-

tule; placochromatophores divide along the transapical plane of the frus-

tule or, if only one plate exists, in longitudinal direction of the frus-

tule. In any case, both halves must -- if their position in the frustule

at rest is along the zone -- also withdraw,either shortly before or after

division, within the borders of the valves from where they return to their normal Aposition after cell division has been completed. Usually just before com-

pletion of cell division, formation of the new cell walls sets in. A plasmatic

partition starts to grow from one or both ends, or even from the entire

circumference, finally .dividing the frustule; it is immediately differ- 43. entiated into two lamellae which assume the structural characteristics of

the particular species and, simultaneously, undergo silicification. In

species leading a solitary exiÀtence,complete separation of the two new frustules can then already take place, since the components still missing

in the younger half. -- connective zone and, possibly, interstitial bands -- can be formed later on; often, they are anyway formed only just before the next division. In the mother frustule, all appendages, nodules, and horns

-- as far as they follow pervalvar direction and i do not exceed the length

of the frustule -- are formed together with the new valves. The very

long setae of the Chaetoceros species, standing at an acute angle to the

pervalvar axis,are, naturally, formed later on; they are pushed out, so

to speak, from inside the frustule by the plasma and silicify during this

process. The last phase of cell division is probably the excretion of the

pectinous membrane*.

We have seen that the new valves are formed on the inside of the

the original silicon walls which provide,in the space formerly enclosed by

new frustule halves,always the "pillbox bottom" for the daughter frustule,

and the "cover" part for the mother frustule. In other words: The epivalve

of the mother frustule receives a new hypovalve, since its original hypo-

valve becomes the epivalve of the daughter frustule and is,as such,also

supplemented with a new hypovalve. However, since the inserted bottom

part of a pillbox-must be smaller than the overlapping cover by twice the

thickness of the latter's wall, one daughter frustule is ) theoretically,a1-

ways smaller . by twice the thickness of the zone than the previous one,after

each'cell.division. Concurrent division of all frustules originating from

*) Translator's note: Called "coleoderm" in pertinent English publications. 44. the same mother frustule would therefore lead to a rapid reduction in size as can be seen from the following Table in.which the letters a - g represent the daughter frustules that would be subject to reduction. We then have: abcdefETotal Mother frustule 1 1 after 1st division 1 + 1 2 after 2nd division 1 + 2 + 1 4 after 3rd division 1 + 3 + 3 + 1 8 after 4th division 1 + 4 + 6 + 4 + 1 16 after 5th division 1 + 5 + 10 + 10 + 5 + 1 32 after 6th division 1 + 6 + 15 + 20 + 15 + 6 + 1 64

Hence, the total number of frustules grows rapidly according to the binomial law, and particularly'in favor of the smaller frustules,so that an absolute minimum would soon be reached and, hence, the limits of vi- ability. However, concurrent division of all frustules from the same ge- neration is very hard to prove in solitary-living species, and observa- tions on concatenations speak against concurrent cell divisions which would have to be stipulated on behalf of the theory of a rapid reduction in size. Concatenations of various species (e.g., Meloseira chains, Fra- gilaria and Eunotia filaments) show without difficulty that, in most cases, the member frustules differ considerably in their state of growth and that, hence, the.time of division also varies. However, even more important is

the fact that the zones have a certain elasticity and their giving way to hllow formation of the new valves suffices to limit reduction to a minimum;

indeed, a difference in size,even between upper and lower valve of a frus-

tule is barely noticeable. If interstitial bands exist, they too may con-

tribute in some cases to achieve the equalization of epi- and hypovhlves.

A Fragilaria filament consisting of approximately 2,000 frustules and, hence,

representing at least 11 levels of cell division, shows hardly any size

differences. This argumentation applies only to species with thin valves,

but this includes a great part of the Diatomaceae; the situation is quite I I mother Translatôr's note

. L..j • This, di ao;ratn ; w,as drawm ...... , .^ , ...... after . Ist division (2) . tip py, th.e. tx',nsl ator. in prder to, be. abld tç translate j this: , ,.,,• ,,,,,,, after 2nd division (3) ' one frustule et rest , ,^)assap,Q on t?re . . . ! ' . ^ ! . ! . . , . . . . bas , s' qf à better : i i i,! ; i . , l^ndor,st.andinm ;f . I . . . , , . . . ,:.. . :.....:.....'..•....'...... '.. after 3rd division (5) ^f the - orâ_^inal one frustule ut rest . . i ^ ' • , . ^ .

. . . . • , , . , , .

réat ...... 4 • . = ...... after 4th division (8) two frustules at rest , . . • ' , . . . . . • , .^ . . ..

^..,.,...,. âfter 5th division (13)_ tht•ee frustules at rest

Çraphic presentntion of Table on p,45 of,translation (p.29 of original)

1 Cell division .in Pleloseir>a arenari 45. different in forms that have thick valves. Reductions in size are obvious seen in and easily spotted in cell accumulations such as A Meloseira arenaria. But is A this, preciselY'itt he species in which Otto ALLER discovered a different mode of cell division. Here, succession is such that only the larger of the two frustules resulting from each cell division divides again, whereas the smaller frustule rests during this divisional period. In other words, the larger frustule resulting from the divisional period n divides again in the (n+l)st period, while the smaller frustule divides only in the

(n+2)nd period. The consequences of this mode of division are shown in the following Table listing the results of 6 divisions:

abcdeTotal Mother frustule 1 1 after 1st division 1 + 1 2 after 2nd division 1 + 2 3 after 3rd division 1 + 3 + 1 5 after 4th division 1 + 4 + 3 8 after 5th division 1 + 5 + 6 + 1 13 after 6th division 1 + 6 + 10 + 4 + 0 21

Here, the total number of frustules grows,according to the recur- rence formulal from one to 1, 2, 3, 5, 8, 13, 21 and so on. Each genera .- tion consists of the total of the two previous generations so that the to- tal number grows much more slowly than under the binomial law, when increa- ses result from the exponential series of two. The difference lies mainly in the number of smaller individuals which amount, from size c on, to 66.6% of all individuals after the 6th division, but to nearly 907, under the bi- nomial law. It is,therefore,obvious that this mode of cell division offers a' way to prevent rapid reductions in size. It is probably much more common among the Diatomaceae than could be assumed on the basis of both these ex- amples. However, this is hard to prove and then 9n1y if the valves show morphological characteristics that would allow grouping the accumulated 46.

frustules according to age; in the species mentioned-[Nleloseira arenaria]

0 this is indeed possible on account of peculiar,reinforcement rings. Fur- 0 thermore, in Eunotia didyma, I was able to determine the sequence of cell division under the binomial law with the help of the reinforcement rings

existing also in this species. However, in principle, there is no way

to completely prevent the size reduction due to cell division; therefore,

G it must be possible to restore the size of the frustules after a certain 0 number of di•visions.âgain to that.of the original frustule through rege- neration. This is the purpose of the auxospores which shall now be dis- 0 cussed in detail, but first I must point out certain consequences of cell rpi division that are of fundamental importance in systematics, as I have p.30

briefly mentioned before [p.44]. On account of the elasticity of the

connective zone, the poles of the transapical axis are under less stress

when the bands are stretched, that is, there is more leeway than at the 0 poles of the apical axis. It follows that, in the course.of cell divi- sion, the length of the apical axis is more reduced than that of the trans-

apical axis; hence, as a rule, smaller individuals_are relatively broa-

der than large forms of the same species. This, in turn, entails a va-

riation of the poles of the apical axis; for example, in relation to their

length in smaller frustules, the acute poles of large individuals change,

with increasing valvar width^gradually into blunt rounded poles, or the

beaklike prolonged poles of the original cell become gradually shorter

in the daughter frustules and may even vanish completely in the smallest

frustules! A distinct delimitation is impossible in all these cases be-

cause even the original frustules show already differences of varying de-

gree, and hence, a certain latitude is bound to show itself in the modi-

fications of form. It follows, however, that these modifications are dic- 47.

tated by the laws of cell division, and deviations cannot be considered either as variations in the genetic sense or as physiologic forms, and hence, their designation cannot be justified. Before a new name is given

to a form deviating from the customary appearance of a species, not only beginners but every expert as well should carefully investigate whether

the questionable form may not, in fact, represent merely a modification caused by cell division. This would considerably disburden the perti- nent literature which is overcrowded with "variations:"

As mentioned before [p.46], the maximal size of a species is re- stored by way of auxospore formation; these go through an unsilicified phase during which their growth is not hindered by rigid walls. Details of their formation are known only of relatively few Diatomaceae; we owe the most essential results to L. GEITLER who has undertaken systematically conducted investigations for the past three decades. Here, I can only re- fer to his reports since a detailed discussion of these aspects would by far exceed the purpose of this booklet. Auxospore formation is basically a sexual process, but it is subject to multifarious modifications within the various groups and, in some, it is even reduced to the point of asexu- ality.

In the Centricae, the process of sexual reproduction'is normally the following: In one vegetative cell, four nuclei are formed by reduction division; three of these perish, whereas, in another vegetative cell, all four of the also haploid nuclei remain intact and provide the basis for four flagellated spermatozoids. Thus, the first cell corresponds to an oogonium containing one ovum, and the second to an antheridium which opens after maturation. The spermatozoids approach the oogonium and enter,,through 48.

an opening,the ovum which may in other instances have been exposed pri-

. or to this approach by a gap n. the mother frustule. The diploid chromo-

somal state is then restored by fusion of the two gametes; immediately

after fertilization,a pectinous membrane forms around the zygote which

grows considerably until it has reached approximately the maximal size

for frustules of this species. Thereby, the wall of the oogonium breaks

if the zygote should still be inside the mother frustule, and the zygote

is either freed completely or remains stuck with an umbonal elevation in

one halve of the mother frustule. Inside the pectinous membrane (called

perizonium) 7 the two siliceous valves of the first frustule of a new series soon appear; of succession the connective zone is formed later, prior to the first A cell division. of The observation , flagellated spermatozoids explains probably- also A the numerous flagellated swarm spores of the Centricae observed already

for quite some time. They have been designated as microspores, their true

nature and subsequent development remained unknown. In some cases, they

probably may also be spermatozoids (male gametes); whether this is always

the case remains to be seen.

The auxospore formation in the Pennatae differs in some respects.

from conditions in the Centricae, but it may nevertheless have derived

from the latteras the modifications seem to be in proportion to the also

different mode of life. Normally, two parent frustules produce two auxo-

spores by paired copulation. The two vegetative frustules assume a dis-

tinct side-by-side position and this initiates the first step of the ma-

turation division of. the nuclei. Division of the plasmatic cbntents. of

the frustules including the chromatophores takes place simultaneously 49.

with the first, but more often after the seconde maturation division. Thus,

in each frustule, two gametes are:formed inside of which the reduction di-

vision takes place resulting in the formation of one macronucleus and one

micronucleus each. If the plasma divides only after the second maturation

division e two macro- and two micronuclei are formed in each frustule. The

micronuclei always disintegrate later in the plasma, while the macronuclei

develop into gametic nuclei. In most of the species observed) the two pa-

rent frustules are enveloped in a common, spacious, gelatinous mass; in

very few cases a special copulation path is formed between the center of

one frustule and that of the other. After formation of the gametes is

completed, two zygotes are produced by fusion of gamete pairs whereby

the gametes behave quite variably, partly isogamous and partly anisogamous.

In the first case, all four gametes actively approach their partner; in

the second case, two gametes each retain their position, they are the

"resting gametes," the two remaining ones are the active "mobile gametes".

Thereby, it is possible that both gametes in a mother cell are either of

LI the . resting or of the mobile type, or that one of them is a resting and

the other a mobile gamete, so that the two zygotes maye therefore.e be formed

either in one mother frustule, or that each frustule produces one of them.

Whether, here, anisogamy is always synonymous with sex differentiation is

still undecided for the time being e because not all Diatomaceae -- as far

as they were studied in this respect -- proved to be constant as regards

the behavior of their gametes.

As mentioned before [p.47], auxospore development is subject to

modifications which can be dealt with only briefly here; è.g.,.in some LI species, each pair of parent cells may produce only one zygote, in other

cases, fusion with the gametes of another frustule may not take place but Q.

both gametes of one frustule may unite and form a zygote, or they may

without copulation -- form two zygotes. Furthermore, the presenee Of C

second parent frustule to initiate nuclear division is not always neces,

sary; some instances are known in which even solitary frustules produced

auxospores. Finally, it should be pointed out that racial mutation ellsP

plays a role in species with variable auxospore formation.

The form of the sporangial frustules always differs more pr less

from that of the vegetative frustules. Particularly the sporangial fruse

tules of the Pennatae are frequently marked by irregular shapes, warpage

and other deformations, and the normal species-specific form is roPtored

only gradually in the course of subsequent cell divisions; the idePeltY

of the first sporangial frustule can often be determined only with eree

difficulty. For example, the constrictions at the dorsal side of the

notia species are restored only gradually during subsequent cell d*v:is-i--

ons so that, here also, conditional form changes exist which mue_ :ppe"

be interpreted as variations, ri Among the Centricae, particularly in the pelagic species, resting ri or internal spores (Fig.30, p.52) are known in addition to the auxospores; these serve the preservation of the species rather than its reproduction ri and are, therefore, produced mainly when the particular faced with a deterioration of environmental conditions. In contrast to the

auxospores which, in accordance with their purpose, are produced by'small

individuals, resting spores can be formed by.all frustules. They distin-..

guish themselves by especially thick valves, the absence of a connective

zone, and differ in form and structure from the vegetative frustPies of

the same species; furthermore, their genesis is completely different from

that of the auxospores. The simplest way is the central contraction of 51.

the plasmatic cell contents with subsequent consecutive expulsion of a.

thick-walled upper and lower valve, closely attached to one another with-

out a connective zone. Sometimes a single nuclear division accompanies

their formation so that two resting spores are produced in one mother

frustule. Complex processes lead to pairs of spores, e.g., in Meloseira

species. Hereby, two thin-walled adjacent frustules commence cell divi-

sion; not only the outer valves which are formed first but also the

dividing cell plates responsible for the final separation have a convex EJ structure so that always one convex and one concave valve come forth from

these dividing walls and, hence, each pair of spores consists of a bi-

convex and a convex-concave frustule with thick valves. The resting

0 spores are set free by decomposition of the mother frustules and serve E later as the starting point for new vegetative generations. The resting spores of marine plankton forms have usually a rather bizarre shape which

has no relation to that of the vegetative frustules; they have,therefore,

frequently been designâted as separate genera. The relationships have

been established only recently, but remain still unexplained for some forms.

The resting spores are probably the equivalent of certain stages

in marine diatoms exhibiting a seasonal dimorphism. During the vegetative I period there is a sudden onset of cell division resulting in frustules of deviating structure. They have thicker valves,and possible appendages are

reduced to short, thick remnants. This entails a diminished floating ca-

pacityy, the newly formed stages sink into lower strata but,after a period

of time determined by certain factors has elapsed)they produce again

normal frustules. However,,these forms (known also as floating spores)

differ considerably from the actual resting spores described above. They 52. 11 do not go through an rest ppesâod but continue to multiply by cell division,always,proctucing daughter frustules of the same structure until

the end of the period. Bencs, we are dealing here with genuine dimorphism.

Fig.30: Resting spores; a-c = Attheya d = Leptocylindrus e,f = Ceratâulina

0 0

Variability p. 33

There is hardly any group of organisms that could equal the vari-

ability observed among the Diatomaceae, but neither is there a group in i which the designation of deviating forms has led to similarly dilettantish 0 blunders even until now; these designations no longer depict speciesbut mere individuals as taxonomic units. These form changes are due to the

mode of cell division characteristic of diatoms and to théir sensitivity

to certain ecological factors; furthermore, there are some species in

which a more or less pronounced variability is inherent,the causes of 53.

which are unknown but it-leads, nevertheless, to the development of

many variations between Cannot -draw the line, so that they also

lack taxonomic importance. The form changes due solely to cell division

have already been discussed under the previous heading [p.41], but they

relate in part to the auxospore stage during which a reaction to environ-

mental influences is possible until silicification of the first valves

is completed. However, with the fully developed valves, the outcome of

the next generation is unalterably determined and not subject ta additi-

1.41i for onal variations except i the form changes due to cell divisions. Mechani-

cal interference during the auxospore stage results frequently in defor-

mations which are inevitably. passed on to the first pair of valves. The

resulting anomalies continue, on account of the silicified cell walls, as

"teratological" forms throughout the whole series of successions, thus

giving the impression of a "variation;" however, they are of no taxono-

mic value, and the normal form is being restored in the event of another

auxospore formation. The influence of physical and chemical envirOnmen-

tal factors upon the auxospore are similar but there is one essential dif-

ference: As long as the environmental factors remain the same, the resul-

ting changes will also persist in subsequent generations after each auxo-

spore formation,instead of 'returning to the original form as is the case

in the aforementioned anomalies. This can be achieved only when the in-

fluence of the ecological factors,which elicited the form changes,is eli-

minated, and recurrences which may follow sooner or later are proof that

these deviations never were genetically fixed "varieties" or "variations"

but represent only ecology-dependent forms.

Nature provides a great number of examples which demonstrate the

physiological effect of ecological factors upon the form of a cell. Ab-

normal forms have been observed for quite some time among Eunotia lunaris, 54.

a species commonly found in fresh waters; here, the.anomalies are due mainr

ly to the high hydrogen-ion concentration in a.cid swamp waters. The in-

fluence of the NaCl-content upon the form of the frustules is easily ob.

served in field samples,without the help of cultures. Higher salinity ma-

nifests itself in some species by its stimulating influence upon the size

of the frustules, and again,in other diatoms by its effect on the form of

the valves; for example, in fresh-water species with constricted capitate

ends which change their form with increasing salinity to lanceolate valves

with acute rostrate apices. Of course, this does not cancel out that spe-

cies having• valves with caz ÿtate apices can occur also amotig truly marine

Diatomaceae; the sea is their native habitat and they are genetically

conditioned for the local degree of salinity. lie must,anyway,beware of r-^ generalizations; every species has its specific charac.teristics not only

as regards its shape but also with regard to physiological aspects. The

manifestations brought forth by ecological factors do not necessarily

have to repeat themselves in all species sharing a particular biotope.


Basic data for an ecological characterization -of the species,

that is, for autecology, can be obtained only by physical and chemical

0 in-depth analyses of the environment, double-checked and supplemented

by comparative investigations of as many bodies of water in diverse ge0s-

► -graphic regions as possible; it goes without saying that, in some in-

stances, additional physiological laboratory tests can be advantageous

despite the fact that the exact conditions of the natural environment

cannot possibly be duplicated in the laboratory. Whole complexes of

factors a'ré'at work'ïn'nature and the ecological factors within these 55.

complexes are more or less dependent upon one another. The degree of

this interdependency is only known in part, and then only with regard

to physicochemical asputs while hardly anything is known about its

effect upon the world of organisms. To arrive at a true autecology of

the species, all forms would have to be examined in relation to all

possible factorial variations, and this would not only be quite impos-

sible even in the case of a single species, but also absolutely sense:- u. less. Therefore, we are forced to investigate each factor separately as an absolute; this can lead to adequate results provided that, as has

just been emphasized, comparative material from various regions is avail-

able in the largest amounts possible. The greater the number of inves-

tigated and chemically analyzed (!) bodies of water, the greater the prob-

ability of covering the factor combinations occurring in nature, and this

is what really counts and not -- at least not for our purposes -- the

reactions of the diatoms in solutions that do not exist in a natural ha-

bitat. This does not question the value of such investigations in re-

search projects concerned with other biological processes;

a) Hydrogen-ion concentration

One of the most important ecological factors in a body of fresh

water is its hydrogen-ion concentration, in short, the pH-value. Some

biologists question its importance because it is, in itself, a conditio-

nal factor, and the influence upon the vegetation in our waters attribu-

ted to it must, therefore, be traced to other causes. However, it has

not been proved that the conditional factor could not also become a con-

. ditioning one; on the contrary, some observations point to this possi-

bility. For example, .waters with a low 'DU-value due to humic acid are 56.

characterized by the limited variety of their diatom vegetation repre-

sented predominantly by species of the genera, Eunotia and Pinnularia.

A similar vegetation -- although composed of other species of both these

genera -- is found also in mineral acid waters (in solfataras of the In-

sulinde*, and of El Salvador) in which the pH-value is also very low,

but for entirely different reasons. There can be hardly any doubt that, here, the pH-value acts indeed as a conditioning factor. At least,

all observations have shown that the neutral pH-value of 7.0 is the ut- most limit of tolerance for many diatoms; hence, as a result of extensive

investigations in the Tropics (the only region with the extreme ecological

contrasts required in this kind of work) the following classification, of

fresh water diatoms only, emerged:

1. Basobiontic forms = biotope with pH ranging above 7.0; 2. basophilous forms = present where pH is about>7.0, optimal distribution at pH 7.0; 3. indifferent forms = evenly distributed around pH 7.0; 4. acidophilous forms = present where pH is about 7.0, optimal distribution at pH < 7.0; 5. acidobiontic forms = biotope with pH ranging below 7.0, optimal distribution at pH 5.5 and lower.

In total, the viability of the diatoms ranges . from pH 2.5 to just

above 9.0, whereby optimal development is observed at about pH 7.5. With

increasing pH-values up to above 8.0,,only a slight decrease has been ob-

served, but declining pH-values are accompanied by rapid decreases, some-

times by leaps and bounds. While the data obtained so far stem from tro-

pical material only, they are applicable also to our geographic region;

In comparison with our alkaline waters are our acid waters inhabited by

only a relatively small number of species also.

*) Translator's note: Insulinde (Lat.-Dutch) is the name given to the host of islands between Southeast Asia and Australia, but is used mainly in reference to Indonesia. rl 1.4 ' o 57. b) Calcium content L. The alkaline character of some of our waters is due mainly to the

presence of water-soluble calcium hydrogen carbonate which plays an essen-

tial role not only as a trophic but also as a physicochemical factor. As

trophic factor it serves as nutritive source of calcium and carbonic acid,

as physicochemical factor it regulates the pH-value on account of its role

in the buffer system by which carbon dioxide is liberated from calcium hy-

drogen carbonate. However, in some waters, the calcium hydrogen carbonate

is widely replaced by magnesium carbonate, but this does not alter the com-

position of the Diatomaceae population which is, in either case, charac-

terized by a great variety of species and a predominance of "calciphilous"

forms. Both salts share a feature essential for the metabolic cycle in our

waters: Both are hydrolyzable and, hence, of decisive influence as regards

the reaction of the water which manifests itself in the pH-value. This

seems to be additional proof that the hydrogen-ion concentration can be-

come a conditioning factor, and it seems questionable whether, as a nutri-

ent for diatoms, calcium can really act as extensively as minimum factor

as Pie seems to be indicated by the distribution of basophilous Diatomaceae.

The total of carbonates contained in the water is designated as alkalinity

or carbonate hardness, and is expressed in "degrees of hardness" (German

degrees of hardness based on 10 mg of CaO in 1 liter of water). Previous

El investigations have shown that, in the Tropics, the development of

diatoms is at an optimum at a carbonate hardness of about 2.8 4.5, that

is, at an alkalinity near 1.0 - 1.6, - or a calcium content of 20-32 mg/liter.

However, noteworthy increases start only at an alkalinity bf about 3.0,

that is, at a carbonate hardness of 8.4, or 60 mg of calcium per liter. 58.

These observations are in agreement with the findings made in the lakes

0 of North Germany, in which the calcium content lies usually around 40 mg f per liter, but the optimum seems to occur at somewhat-higher values than in the Tropics. Beginning at a calcium concentration of about 20 mg/liter

(a hardness of 2.8 and an alkalinity of 1.0), the abundance of diatoms

shows a distinct decline as alkalinity decreases, and acidophilous as

well as acidobiontic species stand out by their increasing numbers so 0 that, in this range of alkalinity, the effect of carbonate concentration seems to be secondary to the pH-value. In the Tropics, the upper limit 0 lies at an alkalinity of about 15.0 or a calcium content of, 0 and thé.nuimber of diatoms able to withstand such a high, or an even higher, threshold value is extremely small. Most of the Diatomaceae u proved to be vastly indifferent to fluctuations in alkalinity; hence, their classification according to calciphobous (having an aversion to 0 calcium), indifferent, calciphilous, and calcibiontic species is, gene- rally, less easily accomplished than a classi:^ication according to pH-

0 values, and usually, it is better replaced by the latter method. Calci-

phobous diatoms are, at any rate, grouped together with the acidophilous

and acidobionti.c forms. ii c) Salinity p. 36 Fo- I The most important salt, from which our waters derive their chlo- s ride content, is the common salt which plays a decisive role in the devel- 9 opment of the diatom flora. It is responsible for the most basic dif- ferentiation of the Diatomaceae into marine and fresh-water forms so that

it becomes a minimum factor for many species, and,•from a certain level

upwards, it even far exceeds all other ecological factors. By far most

of the Diatomaceae are marine forms. Fluctuations in salinity generally 0 59. 0 range --• if we exclude the highly concentrated salines, salt water springs, and a very few lake basins* -- only from 0 to 3.4 %; hence, it is under-

standable that even just detectable traces exert an influence upon the

diatom vegetation. KOLBE classified the halobionts on the basis of the

NaCl-concentration; for logical reasons I have slightly altered his sys-

tem, but only in its form, leaving the salinity values suggested by KOLBE

unchanged. This results in the following grouping:

I. Euha.lobiontic diatoms: Salinity (NaCl, 14gC12) vitally essential; 0 lower limit approximately 570. These in- clude: 0 1. Polyhalobionts; salinity about 30-40%d„ and (in salines) high- er. Therefore,this group is comprised mainly of the marine forms.

0 2. Mesohalobionts; salinity approximately 5%oto around 20%vâ mainly the diatoms designated as "brackish 0 forms." II. Oligohalobiontic diatoms: Salinity not absolutely essential, but tolerated within limits (up to about-5%a), or even beneficial to their development.

1. Halophilous forms; fresh water diatoms upon which a slight 0 salinity has a stimulating effect. 2. Indifferent forms; fresh water diatoms which tolerate a limi- ted degreè of salinity without noticeable ^ influence. III. Halophobous diatoms: fresh water diatoms having an aversion to salt and rejecting even j.ust detectable 0 traces of salinity which 'hindèr develop- ment. To this group belong mainly the spe- cies living in peat deposits.

€ It is of course impossible to draw a sharp line of distinction

between these groups since they overlap one another. Particularly un-

certain are the boundaries of the mesohalobionts which sometimes con- 0 sist only of euryhaline polyhalobionts, that is, of true marine forms

*) Translator's note: E.g., the Dead Sea. 60.

with a wide ecological valence, while, on the other hand, halophilous

fresh water diatoms stray over into the range:of the mesohalobionts. It

is noteworthy that, in general, the euhalobionts can tolerate a certain better decrease in salinityA than the oligohalobionts can tolerate, in the oppo-

site case, an increase. This becomes apparent particularly in estuaries

of rivers in which marine diatoms advance far upstream, while the fresh

water species very soon disappear. Finally, it should be pointed out D. that some of the chloride-dependent forms play a role also in investiga- tions concerned with sewage.

ET d) Nitrogen and phosphorus

Both these elements are among the most important structural con- are stituents of the protoplasm and Alience, also an indispensable nutrient for the Diatomaceae. Sufficient amounts of nitrogen are present in all

waters and it can, therefore, hardly be considered a minimum factor in

the sustenance of diatoms. On the other hand, an increased nitrogen .

concentration -- the precise limit is still undetermined,but lies approxi-

mately at 0.1 mg/liter -- has shown its effect insofar as it causes the

plankton to feature a predominantly Synedra/Nitzschia'vegetation, while

the otherwise characteristic Meloseira species are present only in limi-

ted numbers or even completely absent. Higher concentrations (as they

exist, for example, in sewage) result in toxic manifestations which com-

Il pletely undermine the development of. a diatom vegetation i as I was able

to witness only recently when investigating a sewage drain with a nitro-

gen (nitrate) content of 2.24 mg/liter.

In contrast to nitrogen are the amounts of phospflorus in our wa-

ters only very small so that it often becomes a minimum factor upon which

the presence of some of the Diatomaceae depends. In sewage with higher . 61.

phosphorus concentrations it âlso has a toxic effect. Threshold values

are, for the time being, better not listed since the existing reports are

only of little use.

e) Other chemical factors

It follows from the very fact that the Diatomaceae are equipped

with silicon valves that silicic acid counts as one of the indispensable

nutrients for diatoms. However, it should be present in all waters in

sufficient amounts since, at least so far, thereis no evidence that it

notably influences the distribution of diatoms. The influence of manga-

nese and iron requires also further investigation before its effect upon

the development and distribution of diatoms can be judged. A considerable

iron concentration may lead to toxic manifestations, and locations with

strong iron flocculation are often rather poor in diatoms.

Oxygen is one of the vitally essential elements also for the Di-

atomaceae and it plays, therefore, an important role in the regional dis- within tribution of diatoms A a body of water. Most of the diatoms are eu- they are in stagnant waters they in- aerobes, that is , Aoxygen-dependent; hence,

habit preferentially the upper strata and the shore zone, even the num-

ber of species inhabiting aerial positions is quite considerable.

f) Water current

The just discussed partiality to oxygen is also closely linked

with the distribution in flowing waters in which the variety of species

that make up their diatom flora hardly falls behind that of the flora

in stagnant waters but is, in some regions, even much greater. Special

form types featuring flat frustules_with narrow valves are sometimes ob-

. served, while, on the other hand, species such as Hydroserà triquetra, Biddulphia pangeroni, and Meloseira roeseana long strands in

swiftly streaming waterfalls. Ecologically, a certain similarity exists

between habitats in flowing waters and the surf zone of lakes, apd henee,- the composition of the.diatom flora is often quite similar in both thesp

biotopes. For some of the Diatomaceae, distribution is limited to flowing waters, or else, they find here their optimal development. They are cal :

or "rheophilous diatoms" to which belong; in m11i4ipp tP led "rheobionts"

the above-mentioned species, Ceratoneis arcus, Diatoma vulgare, Actinella mirabilis, and many more. Apart from this selective effect plays water current an important role also in the geographical distribution pf the pia: atomaceae which is not to be underestimated.

g) Temperature

Temperature is the all-enlivening but—in its extremes—also life- destructing factor of towering importance, eliciting not only an indirect overall effect upon other, temperature-dependent, factors, but determining_ directly also the composition of the Diatomaceae flora of a biotope.. The__- direct effect manifests itself in the areas of distribution,in general as_- well as in the restriction of some species to a certain temperature range.

The viability of diatoms lies.generally within the range of near 00 to p.38

40-450C; the limit of 450 is seldom exceeded in natural habitats. I ar: rived at this value already in the course of my investigations pp material from Indonesia, and it was later confirmed by my work in the solfataric regions of El Salvador. Within this temperature range, the diatoms in in- land waters -- and only these are involved -- are differently distributed_ over the individual temperature levels; therefore, a classification of the species is possible for which the terms "stenothermal" and "euryther : mal" no longer suffice since these cannot pinpoint the position within the 63.

temperature range indicated. A stenothermal species may inhabit a cold-

water region or,just as well,a warm-water level; among eurythermal forms,

0 fluctuations of 150, 20° ore more °C are quite possible. Whichever circum- 0 stance applies must come out clearly from an ecological classification. Therefore, on the basis of the temperature fluctuations tolerated by the

individual species (ecological valence), we distinguish four principal

groups of which the first three are to be subdivided according to their

position within the entire range; thus, we arrive at the following out-


Temperature fluctuations of about 5°C; 1. Eustenothermal forms: cold-water forms up to 150C, temperate forms = 15-25°C, warm-water forms above 250C.

2. Mesostenothermal forms: Fluctuations of about 10°C; _ "tropical cold-water forms" = 10-20°C, temperate forms = 15-25 and 20-30°C, D warm-water forms = 25-35, 30-40°C (and more). 3. Meso-eurythermal forms: Fluctuations of about 15°C; cold-water to temperate forms = 10-25°C, temperate forms = 15-30°C, temperate to warm-water forms = *luc- tuations of 20°C and more.

and more. 4. Eu-eurythermal forms: Fluctuation of 20°C

This classification is not just a mere theory but has been pieced

together by the results of practical work on an extensive material; to men-

tion three examples: 1. Biddulphia pangeroni; mesostenothermal, temperate,

found in 83 samples, 79 of these at 20-30°C. 2. Achnanthes crenulata; meso-

eurythermal, cold-water to temperate forms, found in 123 samples, 102 of

Hydrosera tri uetra; meso-eurythermal, temperate, these at 10-25°C. 3.

found in 73 samples, all at 15-30°C.

The number of Diatomaceae tolerating only minimal' temperature fluc-

tuations is very small; the great majority of diatoms of all regions is

composed of eurythermal species whose biotope in tropical regions is main-

ly in the higher, in all other regions predominantly in the lower,tempera- 64.

ture levels. The optimum in the development of fresh-water diatoms lies, 0 on the average, approximately at 26°C, and sli.ghtly lower for the cosmo- politan forms, but somewhat higher for tropical forms. However; even in

0 the Tropics is the maximum in the variety of species already on the de- il cline again when temperatures reach about 30°C, and 40-45°C are tolerated by only a dwindling few; in thermal springs where temperatures exceed

this level, only blue-green algae and bacteria can still be found. Inves-

tigations are difficult to conduct at these locations, since the only sub-

strates•for diatoms are rocks,and whenever these lie outside the principal

mass of water their surface temperature can often not be relinbly me.asuresl..

I have examined rocks,continuously irrigated by a fine mist havin,g a tt*,m-

perature of 50°C,and found them always to be free of live diatoms. It 1B

essential in this kind of work that the -ma-terial is exami^ned as sogn as

possible while it is still fresh; temperature questions canent be ^.olved

on the basis of fixed and possibly only much later exami-ned :fi.eldmafi:exia1 -p••39

since the phantastic values then obtained are entirely unme:ai3Bi.:i_c.

The existence of eustenothermal cold water ma.rine :furms is., a:cr_or- r•.

ding to our experience in the Polar Region, hardly in'doub.t;:however, the

i presence of such species in fresh water has not as been ^as^-tab:l1-5hed 0 with certainty because indications concerning temperature-sare:mis;sing :in nearly all of the relevant report. Therefore,- it can only =n: use the 0 issue if Nordic-Alpine forms are nevertheless identi.fied wi_th _tiiis ,gro.up because, in the summer, temperatures in small puddles which often have

a flourishing diatom flora rises even in Lapland to more than 20°C. In

the distribution of Nordic-Alpine Diatomaceae is temper.ature secondary to

the chemism of the water; it is for this- reason,-tha.t•, -for _exampl.e, -the

flora of calcium-rich biotopes corresponds very much to _that of _telnp.erate 65. regions. The relation of the Diatomaceae to the temperature factor is of

importance especially in geological research and must, therefore, be care-

fully examined in all cases.

h) Light

As for all autotrophic plants, light is vitally essential also

for the Diatomaceae, with the exception of a very few species. Hence, it

not only regulates their distribution in our waters, but it also acts as

minimum factor. However, since light conditions are closely connected

with oxygen and temperature levels, it may sometimes be difficult to de-

cide which of these ecological factors exerts the decisive influence. Di-

atoms able to move about independently are free to seek out locations

which satisfy their requirements for light; in bright sunshine their pho-

toactive reaction is negative l although, in general, it is positive. The

twilight zone of stagnant waters is inhabited by diatoms which flourish

also in shallower waters under more favorable light conditions; hence,

they are,here,first and foremost dependent upon oxygen and temperature.

On the other hand determines light,as minimum factor) the lower threshold

of this zone below which life is no longer possible for autotrophic spe-

cies. In flowing waters it is especially the influence of light upon teffi-

perature which is effective so that, here, this factor is of greater im-

portance in the development of the diatom flora. Sessile Diatomaceae,

particularly the plankton forms, are usually capable of compensating for

too intensive illumination by shifting the chromatophores, which may pos-

sibly entail also a descent into lower strata.

Floatation aids

Many of the Diatomaceae are restricted to a pelagic existence and

must, therefore, be able to stay suspended in certain levels of the water. 66.

The drifting of plankton organisms is actually a desCent at extremely slow speed which is directly proportional to excesS;weight, and in reverse pro- portion to form-resistance and internal friction:

Speed of descent = excess.weight. form-resistance X internal friction Correspondingly, we find the diatoms equipped with structures which either enhance form resistance,or decrease the excess weight (Fig.31). The most minute forms are not in need of such aids, they remain suspended in the water, much like bacteria or fine particles of any kind. To the same ef- fect are flat, discoid diatoms in normal position forming a sufficiently large plane of support which protects them from sinking; but these disks p.40 are frequently further enlarged by gelatin formations (Planktionella, Some

Cyclotella species) whereby also their specific - diminished.

Fig.31: Floatation aids; a,b = Chaetoceros with setae, c,d = Planktoniella with umbrella (d higher magnification of valve only)

a1.111 In many cases, the same is achieved by varying forms of concatenation.

Particularly unique are the setaceouS structures which, in the solitary diatoms of the genus Gossleriella, form a tuft of closely-set setae, while,

in the Rhizosolenatae, a single seta extends from each valve, but these

lead frequently to concatenation and to the extreme case's found among

the genera Chaetoceros and Corethron. Dead 1ndiVi,444 vill stiAk depite

these floatation aids,which shows thnt they ar pt all that is needed . 67.

for floatation, but that physiological processes in the live frustule also

play a part, be it only to maintain the frustules, solitary or concatenate,

in a certain position which most effectively resists their descent.

The opinion that the manifestations of acclimatization to a pela- P' gic life are much more pronounced in warmer waters,appliesr-according to

my observations during the past two decades--neither to fresh waters

nor to the oceans. Some of the plankton forms characteristic of tempera- D. te waters are missing from tropical lakes and are not replaced by others, while, in the antarctic region, concatenation and setae formation of pe-

lagic Diatomaceae sometimes results in extreme forms (Amphiprora, Pseudo-

nitzschia, Nitzschia, Fragilariopsis, Chaetoceros, Corethron).

Nutrition and qDreparation of cultures

Some of the nutritional questiens concerning the Diatomaceae have

already come up in the discussion of ecological aspects [pp.54-61] since

both these factors are closely related. .Only a dwindling few engage in

saprophytic nutrition while all others are equipped for autotrophie ex-

istence. Some can, in addition, derive nourishment from organic . matter,

that is, their sustenance is mixotrophic. Experiments on cultures have

shown that.the.essential anerganic nutrients probably consist of calci-

um, potassium, magnesium, sodium and silicon; all of these can . be

derived from various compounds. The question whether the individual

nutrients are actually interchangeable or whether such mutual substitu-

tion is due merely to osmotic processes seems not to be completely solved.

[: Among the organic elements we must first of all consider nitrogen and

phosphorus which are obtained from anorganic as well as from organic sub-

stances. In culture media, asparagine, albumin, leucine, and peptone El * Translatorts Note: For "anorganic" please read "inorganic" Îl 68.

proved to be the best sources of nitrogen.

The investigation of certain nutritional and vital processes in 0 diatoms requires the preparation of cultures. The composition of the me- dia as well as the experimental design have to be varied depending upon p.41

the purpose of the investigation; there are no standard procedures.

The methods indicated for algae cultures are, for general purposes,

applicable also for diatoms; The following mixture, for which both so- 0 lutions are to be stored separately, proved to be particularly successful: Solution A: Magnesium sulfate 10 g sodium chloride 10 g a sodium sulfate 5 g ammonium nitrate 1 g potassium nitrate 2 g sodium nitrate 2 g potassium bromide 0.2 g potassium iodide 0.1 g 0 water 100 ccm Solution B: Sodium phosphate 4 g . calcium chloride, anhydrous 4 g hydrochloric acid, pure, 22° Bé. ( about 35%) 2 ccm ferric chloride, 450 Bé.,*aqueous solution 2 ccm water 80 ccm

' Solution B is prepared by first dissolving the phosphate in 40 ccm W of water, then adding hydrochloric acid and ferric chloride; without fil- tering o$ the precipitate, this fluid is mixed with the calcium chloride

after dissolving the latter in 40 ccm of water. For the medium itself,

40 drops of solution A and 10-20 drops of solution B are added for each

liter of tap water. Furthermore, 0.5 g of straw and an equal amount of f moss are first sterilized by being dipped into boiling water and then ad- ded to the fluid. Before use, the prepared medium is heated to 70°C; the 0 water lost during the experiments by evaporation is replaced by adding distilled water from time to time.

f *) Translator's note: According to the-Baumé scaleUntoine BAUIvIE, 1768-1804, chemist, inventor of the hydrometer with arbit-rary scales in- dicating specific gravity in degrees [20° Be =331.45% HC1,]). 69.

The following solutions are recommended for marine diatom cultures:

1. Sea salt 250 g 2. Sodium chloride 10 magnesium sulfate 20 g sodium sulfate 5 g magnesium chloride 40 g potassium nitrate 2.5 g water 10 liters potassium pyrophosphate 2.5 g water 100 ccm

Depending upon its purpose, a pure culture of diatoms may .be star- ted either in a Petri dish or in a test tube, with a fluid medium, or on gelatin or agar. Instead of the oldfashioned prepared culture media, de- coctions from the natural habitat are frequently used, sometimes supple- mented with certain nutrient salts. Satisfactory results have been obtai- ned also with the following method: 3 kg sifted, slightly moist, organic soil and 3 liters of distilled water are mixed; this starting-solution is then cooked in a steam cooker for three hours. Three days later, the soil solution is drawn off carefully and filtered; the filtrate is filled in- to Erlenmeyer flasks and the individual batches are then sterilized three times at 24-hour intervals, for 30 minutes each. After about two weeks, the soil solution is carefully decanted into fresh flasks without disturbing the underlying sedimentand again sterilized; this process is repeated once more after an additional two weeks. The standard solution thus ob- tained is to be stored in a cool place until utilization. Just before use,

0.2 g sodium nitrate and 0.04 g of common sodium phosphate are added for each 200 ccm of standard solution and diluted with 1,800 ccm of tap water.

For the solid culture medium, 3.2 ccm of liquid sodium silicate is added p.42 to 2 liters of this solution which is then distributed to the Petri dishes, covering each bottom 2-3 mm high with the medium. Condensation of water on the cover should, possibly, be avoided. 0 70. Collection of material

0 Those who can rely upon an institute ag,a base for their work 0 will find there the 'customary equipment such as pole scrapers, algae rakes, dredges, and plankton nets needed for collecting their material. I may, 0 therefore, concentrate here on things that are of interest to those who, rely First of all, hauing no institutiorial backing,mustnon their own resources.

the equipment should be-light and easy to handle, but also practical and

inexpensive.- It is advised to keep all samples in wet condition until

they can be evaluated, since dehydrated material is subject to losses because

fragile and large forms tend to break when later soaked. Therefore, un-

breakable wide-necked bottles are best suited for transportation; a ca-

0 pacity of 4-5 ccm fully suffices as it would be senseless to return with

huge amounts of material'which could not possibly be evaluated in a life-

time: Larger samples are taken only of sludge or mud because the quanti-

ty isyhere,usually greatly reduced after elutriation of intermixed mineral

substances. If plankton is required, this should be collected before the

sediment is stirred up during collection of littoral and bottom samples.

If working close to the home, or several days at a field station, it is

advantageous to collect sedimentary plankton as a certain way to obtain

even the smallest forms, which escape the mesh of a net, in sufficient

amounts. It is practical to use plastic bottles since they weigh very'

little; depending upon the amount of plankton expected, their capacity

should be 1/2 to 1 liter. To terminate the life processes of the forms,

a small amount of Formalin is added and the bottles are kept undisturbed

until the next day at which time the water is drawn off carefully and

the underlying sediment filled into smaller jars. Plankton nets of the

sheerest silk gauze are indispensable on longer expeditions. Floating 71. or submerged aquatic plants which cannot be reached by hand are pulled ashore with the help of a small kedge fastened to a long enough line; immediately squeezed out or wrapped,as theyare,in watertight material and prepared at home. Reeds, pieces of wood extending into the water

(foot bridges, branches), and rocks are scraped with a knife. Mud samp- les are collected with a scoop, preferentially homemade from an empty tin can(about 8 cm wide) since the commercially available scoops are usually unnecessarily heavy. A few small holes are punched into the can just above the bottom to let excess water escape, and a handle made from strong wire is fastened to the top and a line attached to it. A small cloth bag is tied to the line, about 20 cm away from the handle; on location, the bag is filled with pebbles so that their weight forces the mouth of the can into the mud. The pebbles are later discarded. In swamps, special attention should be given to moss hags; they usually host an abundance of diatoms and have simply to be squeezed out. Seeming- ly bare or moss-grown damp rocks are to be considered in mountain ranges,

and algae-covered window panes in greenhouses are scraped. Well—shafts and troughs in villages, flowerpot stands that have not been cleaned for some time, and sewage filtration plants are all additional sources which always yield different species and may, thus, enrich our knowledge of their various forms.

It goes without saying that all vital data (location, etc.) have to be attached to each sample immediately. Wherever possible, ecological data should also be added; of these, temperature and pH-value are easily established on location. Complete chemical analyses are indispensable for ecological investigations. u 72. Quite profitable are examinations of the intestinal contents of

aquatic , be they fresh-water dwellers or marine organisms, from

the larvae of certain Chironomidae all the way to the herbivorous fishes.

Many marine forms may be obtainable only in this manner, and it is quite

possible that the examination of only a few fresh-water animals may suf-

fice to obtain the entire range of all Diatomaceae inhabiting a particular

body of water. Usually, these-animals graze on large areas as their pas-

tures, while our method of sampling can only be a "spot-testing."


The collected material requires preparation according to the pur-

pose-it is supposed to servei and needs, perhaps, to be divided accordingly.

Specimens to be used for cultures are, of course, to be kept alive. In

the case of floristic investigations, fixation with Formalin willsuffice

if final preparation cannot follow soon. Investigation of the cell con-

tents requires early fixation with the methods usually employed in botany

and described in relevant textbooks, or in some of the papers dealing with

similar investigations. I shall, here, limit myself to describing only

the acetocarmine method recommended by GEITLER. The solution is prepared

as follows: 45 parts of concentrated acetic acid (glacial acetic acid)

are mixed with 55 parts of distilled water; an excessive amount of approxi-

mately 5 g of a good carmine (e.g., Carminum rubrum opticum, manufactured

11 by GrUbler) is added per 100 ccm of this 45% acetic acid and simmered

over very low heat for 1/2 to 1 hour (if a reflux condenser is unavailable,

a narrow-necked Erlenmeyer flask should be used to avoid loss from eva-

poration). After the saturated dark-red solution has cooled down com-

pletely it is decanted into a storage bottle. The excess carmine is re- 73.

usable after drying; any carmine that might precipitate later on has to

be removed by filtration. Since fixation is frequently unsatisfactory,

prefixation with a suitable substance is indicated, e.g., a mixture of

alcohol and glacial acetic acid prepared as follows: 2-3 parts of abso-

lute alcohol are mixed with 1 part of concentrated acetic acid, but only

just before use since, otherwise, decomposition occurs. Instead of ab-

solute alcohol, 96-98% alcohol may be used without unfavorable effect,

even the mixing proportion is usually not of great importance; in gene-

_ral, it is best to start with a 3:1 solution, and to change this propor-

tion if results are unsatisfactory. The material must either be sudden-

ly immersed into the fixative, or the latter must be poured over it quick-

ly. This method is particularly suited for the study of nuclei and chro-


Chromatophores, assimilation products, and gelatinous structures

are best examined on live diatoms if the object is to determine their number

form and position. In vivo staining with soluble aniline dyes and moun-

ting in India ink suspensions is a very good method to bring out the -

gelatinous structures. At any rate, inspection of live material prior to so as any acid treatment is always advisable to check for possible concatena-

tions which are often separated in the course of subsequent preparation.

The determination of species, however, is usually possible only after de-

struction of the cell contents which renders the structure of the valve

better visible; it is therefore always desirable, even for investigations

of another nature, to prepare part of the material according to the methods

described under the next heading. N


Preparation of raw material

Removal of the cell contents can be achieved either with acids or

by the ignition process. However, the latter method should possibly be

avoided since it destroys also the markings of the valves of the more

delicate forms. This technique may be replaced by another method which

will be described later [p.75]. Furthermore, specimens with delicate

valves tolerate boiling in acids - except for the segmentation of

the frustule, leaving its individual constituents -- better than the

incandescence involved in the ignition process. Therefore, I shall dis-

cuss here only the treatment with acids.

The raw material is sifted to remove all coarse foreign matter,

and freed from sand by sedimentation; subsequently, it is left in a bea-

ker for several hours, preferentially overnight, for the sedimentation

of the diatoms. The water above the underlying sediment is then decan-

ted as completely as possible and replaced with concentrated sulfuric

acid until the acid level is at least 1 cm above the sediment. Boiling

should best be done under a fume hood in a sand bath, or outdoors on an

electric hot plate, for at least 20 minutes. Depending upon the size of

the sand bath, several samples may be treated simultaneously. After the

time allotted, potassium nitrate is added in small amounts to the still

boiling acid until the previously black mass is completely clear. After

cooling and allowing the diatoms to settle, the excess acid is carefully

decanted and the sediment washed repeatedly with tap water. The last rin-

sing is done with distilled water which is used also for storing the dia-

toms until further preparation. If this cannot be done immediately, a

few drops of Formalin are added for conservation. Less contaminated ma- ,


terial may be treated with nitric acid instead of sulfuric acid, in which

case decoloration with potassium nitrate is no longer required, but spe-

cial care has to be taken that the acid does not boil down completely.

Boiling with corrosive acids is an unpleasant task because of

the fumes which develop; it is,therefore)impossible for many a hobbyist

to do it at home. Hence, a cold process has been adopted in recent years;

it can- be done in closed rooms andin the majority of casesy-the--results

are-quite satisfactory. After freeing the material from all useless foreign

matter it is, here again, placed in a beaker whereupon concentrated sulfuric

acid is poured over it. Even distribution of the material in the acid

can be achieved either by stirring with a glass rod or by back-and-forth

0 decantation. A minute amount of a saturated potassium permanganate solu-

tion is added, and the mixture is repetedly-decanted whereby it becomes

a hot mass and assumes a blackish-purple color. Now, an also saturated

solution of oxalic acid is added until the substance is clear, which hap-

pens momemtarily; after shaking it well again, the beaker is filled up are with water, the contents„again decanted and then allowed to settle--(ur- Hi gent cases are speeded up by centrifugation). The entire procedure takes a few minutes (not counting settling and elutriation) and is easily re-

0 peated if, for some reason, purification is incomplete. It should be a

standing rule always to treat only a small amount at a time and not to

economize on acids! When employing the cold process, it is important

not to add too much potassium permanganate since, otherwise, insoluble

crystals form among the sediment and, while they do no harm, they are

not welcome on the slide. This method also has the disadvantage that

many frustules are not segmented and, hence, come to lie on their con- 76. nective zone when mounted. However, this "disadvantage" is rather ad- vantageous in the case of forms with discordant valve structures (e.g., among the genera Achnanthes and Cocconeis) since the undetached valves clearly show that they belong together, that is, that both come from one same frustule. and theeevertheless, if separation of the valves has to be achieved

(e.g., of Fragilaria, Eunotia, and Pinnularia specimens), the hot treat- p.45 ment (like it or not) will have to follow the cold method. Great care

is indicated while working with sulfuric acid, since acid spurts may

cause serious injuries (careful when mixing sulfuric acid with other liq- uids!).

Sludge, rich in calcium, requires pretreatment before submitting

it to the sulfuric acid method to avoid formation of calcium sulfate

crystals which would seriously interfere with subsequent analyses. From are added time to time, a few drops of hydrochloric acid,to the water with the un-

derlying sediment,until evervescence ceases. To avoid foaming and pos-

sible loss of diatoms, the water is topped with a few drops of alcohol by

letting them run along the inner wall of the beaker from a pipette. Af-

ter removal of the hydrochloric acid by elutriation, subsequent treatment with one of the methods described in the literature lollows.

Dry material such as moss, stems of plants, and lumps of dried-out

mud are first boiled up in water to drive out air from the frustules and

to accomplish their sedimentation. In particularly stubborn cases (solid

mud), one tablet of perhydride or a few drops of concentrated hydrogen per-

oxide are added to the water.

As for fossil conglomerates, we must diatinguish between two types:

1. Earths, breaking up easily in water, 2. solid rock formations that can- 77.

not be broken up in water. In the first case, the material is first boiled

up in water and then treated with the same methods as are £resh samples;

in a similar manner, limestone is made to disintegrate with hydrochloric

acid. All other rocks are crushed mechanically into small pieces and

transformed into a semifluid pulp with one of the following methods:

1. The crushed pieces are boiled in water to which several tablets of per-

hydride have been added to obtain an approximately 10% solution. 2. The

material is placed into a porcelain dish, and a hot supersaturated Glauber

-salt* solution is poured over it. After cooling, a few crystals of this

salt are dropped into the solution. The crystallization subsequently

taking place in the solution causes the material to burst and by repea-

ting this process,it is finally reduced to a pulpy consistency. 3. The

same can be achieved during the subzero weather of winter by repeated

freezing and thawing out of the material after starting the procedure by

pouring very hot water on it. Further preparation of the pulp takes place

in the usual manner; when using Glauber salt, this has to be removed by

elutriation prior to the treatment with acids.

For final storage of the purified material it iS best filled into

small, rimmed, test tubes about 6 cm long and 1 cm wide, which

are then sealed with good corks. Water with a few drops of Formalin ser-

ves as the fluid which is protected from drying out by the addition of 1-3

drops of glycerine, depending upon the amount of sediment. A label is at-

tached to each tube on which the data pertaining to its origin are marked

with India ink (it is strongly advised against re ) lacing such data by enu-

meration with reference to a separate listing, since loss Or misplacement

of the list would render the collection Worth less!). Larger collections

*) Translator's note: = Sodium sulfate decahydrate. 78. have also to be numbered successively and catalogized so as to be able to lay hands on any desired item at any time.


We distinguish: 1. Composite slides showing the multitude of forms found in any one material in a random manner, and 2. slides with selected individuals in fixed positions, as single, sectorial, or stan- dard samples of types. The selectioh and positioning of individual spe- cimens requires a special apparatus, a great deal of skill, and an enor- mous amount of time which is better devoted to the actual investigation while leaving selection and positioning to.trained technicians. ** This discussion is therefore limited to composite slides which, in general, fully serve the purpose of our work. Storax, hyrax, or pleurax are the mounting media which are almost exclusively in use today; the solvents for the two first-mentioned media is xylol, but it is acetone or alcohol for the last-mentioned medium. Hyrax and pleurax are synthetic resins manufactured in the U.S.A.; their refractive index is higher (1.7 - 1.8) and they are, therefore, indispensable for the analysis of finer struc-

tures, while the natural storax*, having a refractive index of 1.58, is particularly suited for coarser forms, but suffices also for the exami- nation of the majority of Diatomaceae species. All solutions used should have only a - modèrately viscous consistency so that they can easily enter the cavities, thus driving out the air; application is the same in all cases. Unfortunately, the manufacture of "Caedax 547" (refractive in- dex = 1.623), developed by the Bayer Company in Leverkusen, Germany, and recommended in my earlier publications, has been discontinued.

*) Translator's note: Storax (as it is called in pertinent English publications, instead of "Styrax" as in the German original) is a resin derived from various trees of the genus Styrax (e.g., Styrax officinalis). *er) See additional note by the author (German original p.64) on p.110 of translation. n,' 79.

The glass slides on which the specimens are to be mounted must

be clean and free of grease (therefore, prior to use best be stored in 0 spirits); they are placed on a thin sheet of copper or aluminum which is then put down where it will be impervious to vibration. The material Ui kept in distilled water (without Formalin and glycerin !) is shaken up, and one drop of it is then diluted with distilled water in a special

little tube, so that the fluid appears slightly turbid. From this di- U lution, one drop each (or more, depending upon the size of the slide) is placed on the glass slides held in readiness. The fluid should imme-

diately spread evenly over the slide and ontb the'edges; if droplets

gather, the glass is not free of grease and cannot be used. After the

water has evaporated (overnight, or on a hot plate at low temperature, in win-

ter on the radiator), the entire batch is briefly heated up at rather

high temperature to remove any trace of moisture from the pores of the

valves; only after they have cooled off completely is the mounting me-

dium brought onto the slides. If there is reason to suspect that air

can be removed only with difficulty from the frustules (e.g., of Melo-

seira), a few drops of pure solvent are first allowed to take effect,

but the mounting resin is added before the solvent has completely eva-

porated. Inspissation is achieved with moderate heat on a hot plate

until, on storax and pleurax, an impression can still just be made with

a dissecting needle, while the hyrax should be completely solid. The

individual slides are then covered with a moderately warm cover glass,

whereupon all preparations are heated on the hot plate until the moun-

ting medium has,in each case,reached the edges all around, and no more

bubbles appear. After cooling off, the cover glass must unmovably lie

in place, and there must not be any cracks in the resin since this would 80. indicate that inspissation was either terminated prematurely, or (if cracks in the medium start at the edges) that it was overdone.

Since acetone and alcohol mix with water, pleurax -- containing one of these liquids as the solvent -- is an excellent medium for moun- ting delicate plankton diatoms which cannot be treated with strong acids, and lose their form, often to the state of indiscernibility, if subjec- ted to the once customary ignition process. The raw material is repeated- ly washed with distilled water until it is safe to assume that all water- soluble mineral substances have been removed (particularly important if material came from saltwater!). The water is-then gradually replaced with pure acetone by repeated washings with the latter. A small amount of the material in it is now transferred into a fresh test tube, and a few drops of pleurax are added to the acetone so that the diatoms are now im- mersed in a greatly diluted pleurax solution. From here, the required . drops are transferred-directly onto the glass slides and allowed to in- spissate for several minutes without applying artificial heat; if neces- sary, more of the firmer pleurax solution may be added, then follows inspissation at low temperature on a hot plate as described above. The diatoms may also be transferred from the acetone directly onto the slide without prior addition of pleurax, which may, instead, be added just be- fore the acetone. has evaporated; however, due to the rapid evaporation of the acetone, this easily leads to agglomeration which is often trouble- some.

The excess of mounting medium surrounding the edges of the slides is removed with a razor blade; the rest is cleaned away with xylol or spirits. A seal of mounting varnish around the edges is not absolutely required, but nevertheless recommended to avoid that, particularly with 81.

the very friable hyrax, the cover glass comes off; besides, some of the

immersion fluids currently in use tend to affect the mounting media. Lii Drawings and photographs A detailed presentation would exceed the scope of this booklet,

but a few hints based on experience might be welcome. The best way to

get thoroughly acquainted with diatoms is to make a'drawing of them, be- are LA cause one is forced to observe every detail;these +*easily missed by just

looking at them. Therefore, drawing is preferable to photographing, at

least at the outset. Since it is important to copy•th' position and num- Q. ber of structural elements with utmost precision, a drawing apparatus has to be used. As a first step, the degree of magnification,depending upon

0 the dimension's,of the customarily used drawing paper, is calculated with D the help of an object micrometer for all the lense combinations to be considered; data supplied with the microscope are useless for this pur- 0 pose. A correspondingly designed table of the calculated data is of per- manent use. The drawing should be of the highest magnification possible,

at least when dealing with dense structures, using just enough light to

render the structures still well distinguishable, and employing round

figures (X 500, 1,000, 1,500, 2.000, and so forth) since these facilitate

easy reading of the species-specific characteristics from the comple-

ted drawing.Unnaturally high magnifications in publications should be

avoided since they are apt to give a false impression of small forms;

it suffices to illustrate delicate structures with a separate higher mag- 0 nification of these details or, in the case of very small individuals,

of entire single valves. Smooth drawing paper, standing up well to era-

sures and suited for pen-and-ink drawings, should be selected, or thin 82. drawing carton with a smooth surface. Paper of good quality is suitable also for etching, but half-tone presentation is to be considered only when niveau differences of the valve are to be emphasized, or if struc- tures must be represented with particular delicacy. Otherwise, pencil sketches are drawn with a medium-soft pencil (about 2 H), and carefully traced with India ink or Scribtol*. For additional details, particular- ly with regard to the illustration of distinct structures, I would like to refer to two of my publications (Microsome, 40, No,5, and 42, No.4).

Drawings require an enormous amount of time and effort, and it is p.48 futile for many investigators to attempt a Élawless reproduction of.par- ticularly complicated structures in form of a drawing; this is where pho- tomicrography can help. A good source of light is essential, and the modern low-voltage microscopy lamps fully serve the purpose. It is less important whether a larger bellows-type camera or a modern compact came- ra with attachment is being used, since both have their advantages and their drawbacks. I personally prefer the compact camera because it works faster and is more economical, and it brings entirely satisfactory results.

It is essential in the case of unstained diatoms that the structural con- trasts,which are usually rather weak, appear as strong as possible in the picture. The best photographic plates for this purpose are the diapo- sitive plates, and, as for films, the hardworking microfilms which have the additional advantage of finer grain; the prolonged time of exposure makes no difference for this type of photography because, even with strong oil immersion, exposure time takes seldomly more than 1/2 second. Wor- king without a blue filter, which -- in most instances -- May be done

*) Translator's note: Scribtol = German brand of India ink. 83.

without causing any harm, further shortens the time of exposure; other

light filters are not of interest. With a bellows-type model, adjust-

ment to a certain magnification is possible, but a compact camera does

not have this feature. However, in order to obtain the desired magnifi-

cation upon subsequent enlargement of the negative without always hav-

ing to measure the-object itself, a picture is taken of the ocular mi-

crometer (whose smallest units usually represent 0.01 mm) on each new

role of film, as well as before every change made in the combination of

- lenses. On a white strip of carton a scale is drwan with India ink,

placing the lines at intervals of 1 cm; this enables the investigator

to adjust the negative very precisely to any desired magnification. When

the graduation of the micrometer coincides with that of the scale draw-

ing, the magnification is 1,000:1, when 10 marks on the scale cover 5

micrometer marks, it is 2,000:1, and so on. The films are developed ac-

cording to special recipes, or with commercially available compounds;

white glossy paper is used for the prints, since it gives the best image

of the delicate structures.

The importance of the Diatomaceae

The diatomaceae represent an essential metabolic facture in the

natural community; aquatic life would not be possible without them. They

also form part of the food chain which is all the more lucrative the grea-

ter their part. On account of population growth and the enormous indus-

trial development the pollution of lakes and rivers rises in all popula-

ted areas at a critical rate. The diatoms are among the organisms which

first and foremost participate in the self-purification of our waters.

Some species occupy even heavily polluted waters and serve as index forms

in biological water analyses; this presupposes, of course, a correct iden-

tification of the species. Diatoms are also of great service in geolo- J 84.

gical investigations and in age determinations of fossiliferous sediments

and contribute, thus, to solving the questions of historical geology.

They have greatly advanced the perfection of our microscopes in their

role as "test objects" which they continue to play in modern electron


The diatoms offer, thus, an abundance of work and problems, but

toil and effort are forgotten over the thrill experienced time and again

by every lover of Nature when her artistry is revealed in these inulti-

facetecl- artz•stic forms.

Tables for determining families and genera , p.49

The scientistswho first focused their attention on diatoms, es-

pecially the master of old in microgeology, EHRENBERG,* distinguished

many genera whose species were later identif.ied:as resting spores of

forms of other genera. Unfortunately, during the recent decades, still

more have been added to the number of such questionable "genera" despite

the fact that, meanwhile, the resting spores had been identified as a

phase in the life cycle of many diatoms, and their variable appearance was

recognized as their characteristic feature. For example, the species

described under MUlleriella V.H., Syndendrium EHR., Stephanogonia EHR.,

Hercotheca E'HR., Xanthiopyxis EHR., Pseudopyxilla forti, and many other

genera are resting spores of marine plankton forms, mainly of the genera

Chaetoceros, Rhizosolenia, and Hemiaulus, whereas some other genera, such

as Macrora HANNA, and Annellus TEPIP., do not even belong to the Diato:-

maceae, but are members of the animal kingdom. Marry genera, especially

fossil forms, are known only from isolated specimens and are frequently

*) Translator's note: Chris. Gottfried Ehrenberg, 1795-1876. 85.

described only insufficiently, so that it is most difficult to identify

them with one of the subgroups; hence, the position of many a genus in

the systematics of the Diatomaceae is still obscure. For the time being,

classification depends strictly upon very superficial characteristics;

however, I am convinced that even the latest synopsis,compiled by KARSTEN

in 1928, requires extensive revisions particularly as regards the Centri-

cae, but this undertaking is possible only after exact knowledge hes been

obtained of the hitherto still insufficiently known genera. In listing •

. the Pennatae, I maintained, for practical reasons, the customary position

of the monoraphedes between the araphedes and biraphedes, although -- in

my opinion -- phylogenetically they derive from the biraphedes and ehould,

therefore, conclude the array of the Naviculatae in a naturel _system of

classification. However, such a revision would diviee the birephedes in-

to two groups set far apart, and since the consecutive order is of po cop-

sequence in our practical work, there is no - harm in meieteining, in this

case, the customary grouping also in future.

The following lists contain most of the genere Imown to eate, but

due to the limited space, a number of genera of the .çentrigee had to be

dropped from it. However, these consist exclusively 10.f. foseeriel speçies,

part of which are not known very well, or are represented only by a sipgle

and usually very rare species. The Diatomaceae cona_ist of two very dis-

tinct divisions:

I. Centrales, or Centricae: Basic form of the valvar plane discoid

to elliptic, valves never bear a raphe ormediàn that woulçl divide.

them into apical sectors, structures are orientated towards the :morpholo-

gical center, or irregular, but never pinnate. By fax:most of the epeçies

are marine forms, a large number are known only from fOss13.s.of the Ter-

tiary period. 86.

0 II. Pennales, or Pennatae: Basic form of the valvar plane linear to lanceolate, less frequently.elliptical to discoid. Characterized by

raphe or median line in apical direction, pinnate structures bilaterally

directed towards raphe or median line, seldom irregular. To this divi-

sion belong most of the fresh water diatoms, but many Pennatae are found

also in saltwater.

The numbers before the name of the genus refer to the illustra-

tions (Italic numerals*to the Plates [p.111-114], the rest to illustra-

tions throughôut the text). 0 I. Centricae p'50

la) Valves without ocelli, protuberance, or processes, but often with longer or shorter spines which usually serve concatenation, surface e of valve usually not divided into structural zones. 1. Family Coscinodiscatae f] lb) Valves with ocelli, protuberances, or processes, or surface of val- ve divided into structural zones ...... 2

2a) Valvar plane asymmetrically elliptic to semi-lanceolate, apical 0 ...... 3 axis curved

2b) Valvar plane formed differently ...... 4

3a) Valves without pseudosepta.• ...... 8. Family Hemidiscaceae

I 3b) Valves with pseudosepta ...... 7. Family Anaulaceae

4a) Surface of valve divided into zones by radial costae or hyaline in- 0 terspaces, or by difference in elevation. 2. Family -Actinodiscaeeae ...... 5 4b) Surface of valve not marked in this manner

5a) Frustules delicate, mostly rod-shaped, with fewer or more marginal bands, without septa, plankton forms ...... 4. Family Soleniaceae

t 5b) Most frustules robust and without marginal bands; if bands present, frustules delicate and valves with short, blunt processes ...... 6

6a) Valves with robust, more or less spiraling, central process, or 0 central part of valve bullose; processes of neighboring frustules intertwine, or bullose protuberances touch one another._ ValvAr plane usually lanceolate, margins of valves usually pronounced den- H ticulate ...... 7 ul- *) Translator's note: Here underlined. 87.

6b) Valves without similar processes 8

7a) Processes spiraling intertwined 9. Family Rutilariaceae

7b) Processes touch, but do not intertwine (Coscinodiscatae e.p.)

8a) Valves with 2 or more usually very long setae, frustules as a rule in filaments, pelagic forms 5. Family Chaetoceraceae

8b) Frustules without such setae 9

9a) Frustules delicate, valves lanceolate,with transapical pseudosepta extending more or less cL?.eply into the valves (Anaulaceae e.p)

9b) Most frustules very robust, valves discoid to elliptical, with ocelli, protuberances (sometimes reduced) or processes 10

10a) Valvar plane predominantly orbicular, less often elliptical,.valves often with ocelli 3. Family Eupodiscaceae

10b) Valvar plane predominantly bilateral to polygonal, valves always with- out ocelli, but with protuberances, processes, or at least different- ly marked polygon angles 6. Family Biddulphiaceae

1. Family Coscinodiscatae,

la) Frustules cylindrical to globular or ellipsoidal, concatenations (most- ly chains), markings predominantly on the usually distinctly developed zones 2 (fossile!),* lb) Frustules single, or ..(-f4D-ss-orà.-al--:-) found only detached, mostly flat and drum-shaped; markings limited mainly to surface of the valve. 14

2a) Frustules in_loose chains connected by mucous threads, or longer hol- low processes, sometimes congregating in gelatinous tubes or amor- phous neste 3

2b) Other forms of concatenation 8

3a) Frustules connected by silicified processes (Sceletonema) 11 Stephanopyxis

3b) Frustules connected by mucous threads, or united in gelatinous tubes or nests 4

4a) Frustules connected by one very thick gelatinous cord Porosira*

4b) Other forms of concatenation 5 p.51

5a) Frustules connected by several separate threads 28 Coscinosira

5b) Frustules connected centrally by a thread, or united in gelatinous tubes or nests 6

'le) Translator's note: It has not been possible to identify this genus from the pertinent literature; this be a nri.nter's error ancitishouLd„ perhaps, rc>crl IIDAA,,, 41- ,à tror "fossorliut please reaa 88.

6a) Frustules connected by one thread each 28 Thalassiosira

6b) Frustules united in tubes or nests 7

7a) Valves with uniformly fine areolation Thalassiosira e.p.

7b) Valves with radiately striated border zone and more or less punc- tate central space 28 Cyclotella e.p.

8a) Valves stellate with rounded truncate arms Hydrosirella

8b) Valves not stellate 9

9a) Valves elliptical Druridgea

9b) Valves circular 10

10a) Structure of frustule wall very coarse, consisting of large polygo- nal areoles 11

10b) . Structure not conspicuously coarse 12

11a) Valves flat, closely united chains 53, 54 Endictya

11b) Valves convex, concatenate, but only at center Pyxidicula

12a) Valves with a central umbilicus, border radiately striated 29 Hyalodiscus

12b) Valves without such center, or striae at border fasciculate . 13

13a) Frustules concatenate, usually in more or less long, free, thread- like chains, markings on valve not fasciculate (Stephanodiscus e.p.) 10, 26 Meloseira

13b) Frustules in short stipate chains, parasitic forms, markings on val- ves usually fasciculate (Phacodiscus?) Podosira

14a) Frustules with a wide extracellular border of a crown of spines, or gelatinous umbrella 15

14b) Frustules withput these formations, at best with extracellular ge- latinous lobules 16

15a) Valves with a wide crown of thickly-set spines, markings very fine Gossleriella

15b) Valves with wide gelatinous umbrella, markings coarse 31 Planktionella

16a) Valves with radial hyaline costae, interspaces finely areolate, areoles at the border alternating in several rows,changing to single row toward center, fresh water forms 41 Stephanodiscus 89.

16b) Valves with different markings, pt°e-dominantly marine forms ..... 17

17a) Frustules with strongly extended pervalvar axis, prolonged cylin- drical with extensive connective zone ...... Ethmodiscus

17b) Pervalvar axis not markedly extended ...... 18

18a) Valves with distinctly demarcated central space with different markings ...... 19

18b) Valves with distinctly differentiated central space ...... 20

19a) Central space surrounded by a ring of large areoles (Heterodictyon) 3 Brightwellia

C 19b) Valves without this ring ...... 7, 8Cyclotella

20a) Central part of valve indented like a bowl, border zone forming G convex rim ...... 2 Craspedodiscus 20b) Valve surface with differently sculptured relief ...... 21

21a) Markings of border interrupted by numerous hyaline radii 20- Cosmiodiscus E 21b) Border zone without these radii ...... 12, 1 Coscinodiscus

2. Family^^...^^ Actinodiscaceae

la) Radial sectors with alternating elevation ...... 2 0 lb) Valves flat or uniformly convex or concave ...... 3 p.52 2a) Individual sectors of border zone again divided by difference in ^ elevation ...... 42 Glorioptychus 2b) Sectors uniform including border zone ...... 11, 12 Actinoptychus LI 3a) Sectors divided by tubules open to the inside and radiating from the center ...... 4 LI 3b) Sectors divided by radial costae ...... 5 4a) All tubules of equal thickness ...... 45 Rylflndsia 46 Asterolampra

f 4b) One of the tubules on each valve distinctly narrower than the rest, valves therefore bilateral ...... Liriogramma 44 Asteromphalus

LI 5a) Valves with robust radial costae And often with shorter intermedi- ate costae and numerous, more or less concentric, transverse costae thus giving the appearance of a web 10 Arachnoidiscus

5b) Markings much finer, valve without spiçier-web appearance ...... 6 90.

6a. Border of valve strongly undulated,horder zone with numerous radial furrows 39 Anthodiscus

6b) Border of valve straight or (very seldolli softly undulated, bor- der zone without radial furrows 15-17 Stictodiscus

la) Structure of valve in sections reminiscent of the back of a turtle Tahulina 34 Cheloniodiscus

lb) Valves without this structure 2

2a) Central space strongly elevated above surface of valve and term 1-' nated by a cown of large robust spines 5 Pyrgodiscus

2h) Central space not emphasized in this manner 3

3a) Valve with one ocellus, more or less close to the border and often difficult to distinguish 4

3b) Valves with several ocelli, protuberances, or processes 7

4a) Valves with coarse areolation, areoles forming three system of straight tangential rows in the center Roperia

4b) Structure not arranged in this manner 5- Li 5a) Ocellus large, close to center of valve 43 Maffiffiula 5b) Ocellus small, often difficult to distinguish, close to border of .- valve 6

- 6a) Valves divided into numerous sectors by radial costae 40 Stictocyc lus U 6b) Valves without these costae 18, 19 Actinocyclus

0 7a) Valves without ocelli, but with more or less numerous (from 2 to 100:), often very insignificant, cylindrical to pearshaped pro- cesses, usuelly extending from elevations 4 Aulacodiscus

7b) Valves with ocelli either on surface or on protuberance

8a) Ocelli small, peripheral 9

8b) Ocelli more or less large, or not close to margin 10

9a) Valves mostly flat, coarsely areolated 9 Eupodiscus

10a) Ocelli On surface of valve, irregularly definded, often tangential oblong Fenestrella 91.

10b) Ocelli sharply demarcated, usually elevated on protuberances .... 11

11a) Valve with central space 13, 14 Auliscus

11b) Central space absent 21 Pseudoauliscus

4. Family Soleniaceae

la) Valves with a single, more or less long to setaceous, usually ex- centric process, with or without barely visible crown of spines'. › 2

lb) Valves without process or, if present, at the border with crown of spines 3

2a) Valves flat, with rudimental peripheral process . Guinardia

- 2h) Valves more or less convex to conical, process distinct, often ex- tended into long seta 7 Rhizosolenia

3a) Valves with marginal crown of spines of two different types Corethron

3b) Marginal setae uniform, not conspicuously long 4

' 4a) Each halve of frustule with only one marginal band being shaped like a collar Bacterosira

4b) Numerous marginal bands, or hardly visible 5

5a) Valves with central porus, opposite pori of adjacent frustules con- nected by a fine thread Schroederella

5b) Valves without central porus 6

6a) Marginal bands hardly visible, valves without markings 30 Leptocylindrus

6b) Marginal bands distinct, valves with apiculi 7

7a) Marginal bands with sharp denticulate ends Dactyliosolen

7b) Marginal bands in the form of a collar 8

8a) Valves with one row of marginal setae only Detonula

8b) Surface of valve with irregularly distributed annuli, in addition with uneven marginal spine .„. Lauderia

5. Family Chaetoeeraceae

la) Valvar plane elliptical, valve with only on e pair of setae 3 1 çhaetoceros

lb) Valves circular, with more or less numerous setae .... Bacteriastrum 92.

6. Family Biddulphiatae

la) Valves with ends elevated or prolonged into horns not tipped with a mucron ...... 2 u lb) Horns- ti-pped with mucron ...... 16

2a) Valves with 2-3 (very seldom more) long processes mushrooming at 0 their free ends ...... 32 Kittonia

2b) Valves without such processes ...... 3

3a) Tri- to multipolar valves ( bipolar variations rare) ...... 4

3b) Uni- or bipolar valves (tripolar variations rare) ...... 9

4a) Valves with long central process ...... Ditylum

G 4b) Valves without this process ...... 5

5a) Frustules in chains connected by fine pervalvar membranes at edge U of valve ...... Lithodesmium 5b) Valves without such membranes ...... 6

D 6a) Chains with very narrow foramina, frustules imperfectly siliceous, markings barely visible, plankton forms ...... Bellerochea

6b) Coarsely silicified litoral and plankton forms ...... 7

7a) Valves with radial costae forming cells, central area not included 25 Entogonia

7b) Valves without such cells ...... 8

0 8a) Marine forms, very extensive genus ...... 30, 31, 94-97 Triceratium

8b) Fresh water forms in streaming tropical waters ...... 28 Hydrosera p.54

9a) Valves only on one po16 elevated into more or less blunt protuberance markings very coarse ...... Isthmia

0 9b) Valves bipolar ...... 10

10a) Insufficiently siliceous plankton forms, markings barel-y-visible 11 t 10b) Frequently strongly siliceous forms with distinct markings, mostly parasitic ...... 14

lla) Frustules without or only slight torsion about pervalvar axis .. 12

llb) Pronounced torsion of frustules and chains ...... Streptotheka

12a) Pervalvar axis straight ...... 13 M 93.

12b) Pervalvar axis more or less curved Eucampia

13a) Pervalvar axis short • Climacodium

13b) Pervalvar axis greatly extended by numerous interstitital bands 30 Attheya

14a) Frustule twisted.on its,pervalvar axis 15

14b) Frustules without torsion 61 Biddulphia

15a) Protuberance sitting on surface of valve 6, 37 Cerataulus

15b) Flat protuberance lies at the zone 26, 27 Huttoniella

16a) Valvar plane circular, processes very short 30 Cerataulina

16b) Valvar plane elliptical or polygonal, processes long 17

17a) Valves with 2 poles 33 Hemiaulus

17b) Valves tri- or quadrangular 50; 51 Trinacria

7. Family Anaulaceae

la) Apical axis curved 2

lb) Apical axis straight 3

2a) Apical axis lunate Eunotogramma

2h) Apical axis sigmoid Helminthopsis

3a) Deep pseudosepta extending.inward, curving, and continuing parallel to the valvar plane almost to the center 35, 36 Porpeia

3h) Pseudosepta formed differently 4

4a) Delicate forms, inner margins of pseudosepta not thickened. Anaulus

• 4b) Very robust forms, more or less pronounced transapical constric- tions, inner margin of pseudosepta usually thickened ... Terpsinoe

8. Family Hemidiscaceae

la) Frustules with more or less numerous interstitial bands, valves.with irregularly spaced poroides 33 Eunotiopsis

.1b) Frustules without interstitial bands, valves àreolate, areoles in. more or less fasciculate radial rows 22 Hemidiscus

9. Family Rutilariaceae

Comprises eight, in part uncertain, fossorial genera, - of which only the most important shall be named: 23, 24 Rutilaria 0 95.

Fig.32: a-e = Entopyla ocellata f-i = Gephyria media a 0 9 C D 0 0 E

0 0

Fig.33: a = Climacosphenia b-d = Licmophora e,f = Licmosphenia

5a) Valves with stout transapical costae, interspaces with finely puncta- te transapical striae, exclusively fresh water forms .. 7 Tetracyclus

5b) rlarkings not differéntiated in this manner ...... 6 96.

6a) Frustules with only two pairs of septa 7

6h) Frustules with more or less numerous pairs' of septa 8

7a) Marine forms, septa usually undulate 8, 29 Grammatophora

7h) Fresh water forms, septa straight 7, 11 26 Tabellaria

8a) Interstitial bands-(zone view!) -show strong markings, marine forms 55, 56 Rhabdonema

8h) Structure of frustule walls fine throughout • 9

9a) Marine forms Striatella

9h) Fresh water forms a: Valves with one central pair of pseudosepta Hustedtiella Vàlves without pseudosepta 7, 11, 26 Tabellaria

10a) :Interstitial bands with one septum 11

10b) Interstitial -bands viith numerous septa 33 Climacosphenia

11a) Septum immediately below head pole of valve 33 Licmophora

11b) Septum at slight distance from head pole 33 Licmosphenia

12a) Valves with stout transapical costae and finely punctate trans- apical striae spaced more or less apart 13

12b) Structure not differentiated in this manner 17

13a) Apical axis heteropolar Meridion ri 13b) Apical axis isopolar 14 14a) Only one valve of frustule with one pair of costae near center of valve Cyclophora

14b) Both valves with more or less numerous costae 15

15a) Marine forms, central space of valve without markings 16

15b) Fresh water forms, central space absent Diatoma

16a) Central space extending to the margin 65 Plagiogramma

16b) Central space not extending to the margin 49 Omphalopsis

17a) Valves stellate with three poles 18

17b) Valves with two poles 19

18a) Points long and slim Centronella 97. Li 18b) Pàints short Fragilaria e.p. 19a) Apical axis arcuate • 20

19b) Apical axis straight or (very seldom) undulate .25

20a) Apical axis heteropolar Campylostylus

20b) Apical axis isopolar 21

21a) Valvar planes of frustule-asymmetrical Campylosira

21b) Valvar planes of frustules symmetrical 22

22a) Markings of valve interrupted along median line by pseudo- . raphe . 23

22b) Valves without psepdoraphe 24

23a) Frustules in filaments Ceratoneis

23b) Frustules solitary Synedra e.p.

24a) Valves with transapical costae, interstices with double rows of alternating areoles, marine forms Pseudoeunotia

24b) Valves with single transapical row of puncta 62 Amphicampa

25a) Frustules forming flat, starshaped colony or adnate ih zigzag fila- ments 26

25b) Concatenation,of a .different nature, or frustules solitary 28

26a) Valves with subtle transapical striae reaching pseudoraphe El 26 Asterionella 26b) Valves with coarse, excentric markings, marine forms 27

27a) Valve endings equal Thalassionema

27b) Valve endings unequal Thalassiothrix e.p. ri 28a) Frustules very long, prismatic, with unequal ends Thalassiothrix e. p.

28h) Frustules with equal ends,or heteropolar distinctly cuneiform .. 29

29a) Apical axis heteropolar 30

29b) Apical axis isopolar 34

30a) Valves with stout transapical costae, interstices coarsely areolate II or punctate Podocystis


30b) Markings finer . ...... 31 . ..... . ...... _ . . . 31a) Interstices between broad . transapical coste Apparently homogen '- ----- ''' (very delicate alveoli ...... ,..... ... ...... Opephora -- 31b) Transapical striae:distinctly punctate or lineeT: 32

32a) Markings not interrupted at median lin e of valve Synedrdsphenia

n. 32b) TransapicaI striae traversed. longitudinally by blank space 33

33e) Valves with different markiPgS at apiçes Sceptroneis

Trachysphenia 33b) Apices hyaline or not especially demarcated - n. 34a) Frustules in filaments 35 34b) Frustules not permanently ip filaments, sometimes detached 41* line, or 35e) Markings on valve not disrupted- by pseudoraphe or median pseudoraphe indistinct 36*

35b) Valves with distinct pseudoraphe and median line 37*

36a) Valves with transapical costae and (sometimes reduced) double rows of areoles (cf. family of Nitzschiaceae[p.1:641`::.- 57 Fragilariopsis

- 36b) Valves areolate without distinct transapical costae Cymatosira

37a) Frustules with pervalvar constriction beneath apices, hence, bands not continuous (one view!) ...... 38* 37h) Valves flat, bands continuous 40 ...... Fragelaria e.p. 38a) Fresh water forms . ... 38b) Marine forms . .....,.. 39 *

39a) Valves with central pseudopodule Glyphodesmis

39b) Valves without pseudonodule Dimerogramma

40a) Valves with transapical rows of coarse moniliform alveoli Rhaphoneis

40b) Valves with finely punctate transapical striae 26 Fragilaria

41a) Valves elliptical to broad lanceolate with trapsapical rows of coarse Alveoli, frustules in filaMentSôr SOlitary -- 42*

41b) Long-stretched narrow valves, markings finer 43* - 42a) Frustules twisted on apical Axis Weissflogia.

*) Translator's note: Numbers with asterisks on this and the following pages refer to illustrations Apparently excluded beCause - of limited space. 99.

0 42b) Frustules without torsion ...... Rhaphoneis e.p. 43a) Valves with short spine before each pole, markings marginal (Ant- 0 arctic marine forms) ...... Thalassionema 43b) Valves without these spines ...... 44*

3 44a) Markings interrupted on either side of median line by longitudinal hyaline bands ...... Clavicula C 44b) Valves without longitudinal hyaline bands ...... 45* 45a) Frustules prismatic, in valve view linear to lanceolate. 11 Synedra

0 45b) Frustules tubular, slightly twisted (doubtful fossorial species) Tubularia

G 11. Family Eunotiaceae

la) Apical axis heteropolar ...... 2

0 Apical axis isopolar ...... 3 lb) C 2a) Apical axis straight ...... 18 Peronia 2b) Apical axis curved ...... Actinella

Branches of raphe dissolved into pores . Falcula, Pseudohimantidium 5 3a)

n 3b) Branches of raphe fully developed ...... 3, 11, 18 Eunotia U 12. Family Achnanthaceae

0 la) Apical axis heteropolar ...... 35 Rhoicosphenia lb) Apical axis isopolar ...... ••••••••••••,••••••• " " " " " " " ' 2

Position of raphe excentric ...... 34 Anorthoneis ni 2a)

2b) Raphe in median line of valves ...... 3 0 p. 59 0 i

a 100.

3a) Frustules with interior stratum of costae (marine forms) 0 60 Campyloneis 3b) Stratum of costae missing or rudimentary,limited to narrow zone at border ...... 4

4a) Apical axis bent (zone view!), frustules usually in filaments or solitary stipitate ...... 34 Achnanthes

4b) Apical axis straight, frustules solitary, not stipitate D 34 Cocconeis 13. Family Naviculatae

la) Raphe placed on keel or wing and elevated above surface of valve.2

lb) Raphe in surface of valve ...... 4

0 2a) Wing sigmoid ...... 78, 88 Amphiprora 0 2b) Wing not sigmoid ...... 3 3a) Transapical axis heteropolar ...... 47, 48 Auricula

3b) Transapical axis isopolar (except for unilateral wings) ^ 83 Tropidoneis ^ 4a) Apical axis or transapical axis, or both, heteropolar ...... 5 4b) Both axes isopolar (rarely with heteropolar transapical axis due to slight shift in symmetry, but these exceptions cannot be con- 0 sidered separately here) ...... 11 5a) Apical axis heteropolar ...... 6

5b) Apical axis isopolar, transapical axis heteropolar ...... 9

6a) Both terminal fissures of raphe hooked sideways-, valves frequent- N -ly somewhat dorsiventral ...... 58 Didymosphenia 6b) Terminal fissure at footpole of valves in prolongation of raphe.7

7a) Transapical axis isopolar ...... 8

7b) Transapical axis heteropolar ...... 35 Gom hocymbella

8a) Branches of raphe very short ...... :...... 63 Gomphopleura

8b) Branches of raphe extended to center of valve . 13, 35 Gomphonema

9a) Pervalvar axis distinctly lunate, frustules in zone view ellip- tical ...... 66, 84 Amphora

9b) Pervalvar axis only slightly curved, zone view usually linear. 10


10a) Frustules in filaments, marine forms Catenula

10b) Frustules do not form filaments, almost exclusively fresh water forms 13, 35 Cymbella

11a) Frustules with intersditialbands,with septa or ring of cells ... 12

11b) Frustules without septa 13

Abb.35: Genera showing heteropolarity; a = Gomphonema b = Cymbella c = Gomphocymbella d-f = Rhoicophenia

12a) Interstitial bands with flat, perforated septa Diatomella

12b) Interstitial bands with ring of cells 7 Mastogloia

13a) Wall of frustule with coarse areolate cells, inside very finely . punctate 80 Dictyoneis

ii 13b) Cell wall with different structure 14

14a) Transapical axis heteropolar (Navicula e. p.) Toxonidea

14b) Transapical axis isopolar 15 II 15a) Apical axis more or less sigmoid 16 15b) Apical axis not sigmoid 17

ri 16a) Markings in two striate systems, crossing at right angles 85 e 86 Gyrosigma

16b) Markings show three systems 15 Pleurosigma

17a) Frustules more or less twisted on apical axis, or, at least, ra raphe in oblique position 18 17b) Frustules not turning about axis 19

18a) Raphe system enclosed between two longitudinal costae 70 Scoliotropis

18b) Valves without the longitudinal costae (Navicula e.p., Neidium e.p.) 69 Scoliopleura 102.

19a) Raphe system enclosed between two longitudinal sulci Diploneis

19b) Valves without such longitudinal furrows 20

20a) Valves with transapically arranged cellS divided by•castae which are crossed by one or several longitudinal bands of inner openings; outer walls apparently homogeneous 21

20b).Frustule wall of different structure 23

21a) Transapical cells in surface of valve divided by more or les wide longitudinal costae 71 8strupia

21b) Cells in valve not interrupted; interruption in connective zone seldom 22

.22a) Markings usually coarse, valves flat, predominantly fresh water forms 4, 16, 23 Pinnularia

22b) Markings finer, valves more or less arcuate, mainly marine forms 72 Caloneis

23a) Raphe system enclosed between two longitudinal costae 24

23h) Valves without these costae 26

24a) Valves lanceolate to oblong elliptical 25

24h) Outline of valve broad rectangular Cistula

25a) Inner terminal fissuresof raphe very long (tropical brackish form) 67 Frickea

25h) Inner terminal fissures short 17, 68 Frustulia

26a) Branches of raphe short, not reaching center of valve 27

26h) Branches of raphe not markedly shortened 29 p.61

27a) Valves with transapical costae and double row of fine pladma pores branches of raphe negligibly shortened Brebissonia

27h) Valves with different markings, branches of raphe more shortened.28

28a) Branches of raphe at a distance from apices Rouxia

28h) Branches of raphe closer to apices Amphipleura

29a) Valve with one or several longitudinal costae in marginal zone, median pores usually with hook-shaped extensions in opposite direc- tions 82 Neidium

29h) Valves of different structure 30 103.

30a) Valves with short costae at margin Mastoneis

30b) Valves without such costae 31

31a) Center of axial part of valve raised as a torus, sudden decline toward margin 32

31b) Surface of valve without such protuberance 34

32a) Marginal zone of valves without markings Scoresbya

32b) Markings include marginal zone of valve 33:

33a) Central nodule and central space extended across the valve, for- ming a stauros Pseudoamphiprora

33b) Valves without stauros (Navicula e.p.) 73,74 Cymatoneis

34a) Central nodule and central space extended into transverse stauros reaching margin of valve, sometimes with cleft 9 Stauroneis

34b) Central nodule and central area independently designed 35

35a) Frustule wall areolate-cellular, outer walls of cells with fine lines of puncta, inside with porus 81 Trachyneis

35b) Frustule wall with different structure 36*

36a) Terminal nodule without external terminal fissures, inner termi- nal fissures in prolongation of raphe Stenoneis

36b) Terminal nodule of different structure 37*

37e) Transapical striae subdivided by more or less undulating longitu- dinal costae, set well apart, so that alveoli are formed which are lengthened in transapical direction Anomoeoneis

37b) Transapical striae more or less distinctly punctate or lineate, structural elements generally not extended in transapical di- rection (Rossia) 10, 13, 25, 75-79 Navicula

14. Family Epithemiaceae

la) Raphe not keeled, inner wall of channel with distinct pores .... 2

lb) Keeled raphe, inner openings of channel indistinct 89, 90 Rhopalodia

2a) Apical axis straight ' 19 Denticula

2b) Apical axis curved 19, 59 Epithemia 104.

15. Family Nitzschiaceae Ev^

la) Frustules spiraling about apical axis ...... Cylindrotheca

1b) Frustules not twisted or only very little ...... 2

2a) Frustule shows mirror-image symmetry in relation to valvar plane.3

2b) Frustule without mirror-image symmetry in relation to valvar plane ...... 6

3a) Transapical axis heteropolar ...... 4

3b) Transapical axis isopolar ...... 5

4a) Apical axis recurved at center, keel in center constricted Hantzschia

4b) Apical axis slightly but evenly curved; keel not constricted Cymbellonitzschia

5a) Frustules unite to platelike colonies; within these, continued p. 62 C sliding of the frustules over each other...... 27 Bacillaria 0 5b) Frustules not concatenating in this manner ...... Nitzschia e.p. 6a) Apical axis heteropolar, frustules clavate ...... Gomphonitzschia 0 6b) Apical axis isopolar ...... 7 7a) Valves with transapical costae and double row of delicate, alter- nating alveoli, frustules always fusiform, usually forming chains, f keel puncta barely distinguishable (cf. Fragilariopsis [p.98] un- der 10th family,Fragilariatae) ...... Pseudonitzschia

7b) Valves have different markings or form, very seldom in chains, keel puncta usually clearly distinguishable .. 20, 91-93 Nitzschia

16. Family Surirellatae

la) Parapical axes of both valves of same frustule parallel to one another or çrossing each other at acute angle ...... 2

lb) Parapical axes crossing at right angle, valves always saddle-, _ shaped ...... 52 Campylodiscus

Parapical axi:^with.several undulations vertipally.arranged on 2a) . ,. surface ot vâivè...... :' ...... 64 ymatopleura

W 2b) Parapical axis straight or curved, but not evenly undulating 6, 22 Surirella



A zomplete list of the entire literature n Diatomaceae would fill

a volume of several hundred pages, although with the reservation that most

of it would relate to phytogeographical treatises which merely contain

lists with more or less numerous, in part unjustified, new descriptions,

whereas useful data of general interest, such as ecological and morpholo-

gical aspects, are dealt with in relatively few publications. Very rare

are comprehensive synopses of systematics but, since they as well include

a "general part," the older literature has already been dealt with here

and is usually cited also in relevant listings. I may therefore refer

to these works and, in addition to these, limit this list of references

to a few important recent additions.

Illustrative publications:

1. ' Pantocseic• • Itar Kenntnis ....t tos. , leu Baci 'Linen lIngarns. Poe ,•, 1880--1892. Vert.. A...I Berlin, 190 2. Pern;rdtb,. Dial.ton"e. 'flaunt., de France et des tlistritis maritimes uisii.. Crez-sur- • I-Mne 1S07 MP's. 3. sehmidP, A . cl. 1)iatiitnactten-Kunde,hegtondet v. :WW1 fortgese...t Schmidt, Fr. 1-'ru* ittiller. II. Heiden end Pr. //tilted,. Asillershlen-Leiprig, 18 7 t -MIL 4. Von iieitnk, if.: S>nopsis des thntontées de Belgique. Anvers. 1880--1885. _ - , _ Synopses of systematics: . . . . • 5. • h.: v...•psis of sertli .-tmerican Dn.ittintaccae. Proc. Arad. Nat. Scient es, Philadelphia, Vol. 78, :t.tilttl 1926.-1927 iithne hh P. 6. c/r,./._ T.: SNnopsi ,, .,t the Navicultud Dutums. Knnel. Sv. Vet. Akad. Ilandl. 26, 27. Stock- 11•.1, 894--1 8°f. 7.. irftstew y.. Stills. asset niatorneen Deutschlancls. Franskh'sdier Verlag, Stuttg..rt, 4. Ann. 1923. 8. : llustedt, Fr. • Bacillariophyta, Paelier, A., Die Süliwasscrflora Mitteleuropas, 11. 10, 2. Aufl. • Jena, 1.9t%' 9. /beget/I. Ur • Dte Kieselalgen Deutsdilatids, osterreidis und der Sdiweiz mit Benitksiditigung der tihrigen Liindt•t• Enropas sotsi. ter atterenzenden istreresgehieto. Rebenhorst, L., Kryp- tcg. Flora Bd. 7. Le:prig, seit 192' unlit ahgesdslossen). 10. Karsten. G.: Bacillariophyta. Engler, A. u. Prantl, K., Die natürlidten Pflanrenfamilien, 2. Aufl., Bd. 2. Leipzig. 1929.

Morphology, biology, and methods

11.. Fogett N.: I -nat iii Water-Cour«in Amen, 1-IV. 1)ansk Bot. Mk. Bd. 12. Knpenhagen, 19-17-19 Pt. Fogecl, N.: Diatoms in the Salt Bog of Langernose in East Forum. - Ebenda, Bd. 13. Koren- lagen, 1919. Fuged, N.: Diatornévegetationen.i Sorte S5. Frits Flora cg Fauna. Bd. 3. Oth•nse, 1950. • 14. Fogrcl. N.: The Diatem Flora of some Danish Springs. Natura Jutl. 4. Aarlitti, 1951. 15. Fob.eti. N.: On the Diatom Flua of 30Mt, Funeu Lakes Fol. Lininol. Scautlin., 6. Kopenhagen, ' 1951. 16. Ceiticr. L.: Per Formwedisel der pennaten Diutomeen. Arch. f. Protistenkde. Bd. 78. Jena, 1932. 106.

, . _ . 17. Ceiller, L.: Zahlreidie Abbandlungen liber Auxt7s-p-orenbildung und Kern- tind gânge in der Üsterr. Bot. Zeitschr. Bd. 95-101. Wien, 1948-1954. Hier audt die übrige Literatur. 18. Geitfer, L.: Samellmethoden der Kehl- und Chromosomenumersuchung. Berlin, 1940 (1. Aufl.). 19. und W. Krieger: Diatomecuschalen lin elektronenmikroskopischen Bild. 1, 1 Berlin, 1953-1954. 20. nusicdi, Fr.: Untersuchungen über den Bau der Diatomeen. 1-12. Ber. Deutsch. Bot. Ces., Bd. 44-53. Berlin, 1926-1935. 21. Husle(11, Fr.: Vom Sammein und Priiparieren der Kieselalgen sowie Angaben über Unter- , stichungs- und Kulturmethoden. Abcierlialcien, E. lianclh. biol. Arbeitsmetb., Alit. 11, T. 4. Berlin, 1929. 22. /fusicat, Systematische und iikologisehe Untersudiungen über die Diatorneen-Flora vmi Java, Bali und Sumatra nach dein Material der Deutsdien limnologischen Sunda-F.xpetlition. Ardi. f. Ilydrob. Suppl. Bd. 15, 10. Stuttgart, 11137-1939. 23. Ilustedt, Diatomeen aus der Urngebung von Ahisko in Sdtwedigh-Lappland. Ebenda, Bd. 89. 1942. 24. Ilastecit, Fr.: Sidhvasser-Diatorneen des indomalayischen Archipels und der Ilawaii-Inseln, Internat. Rev. Hydrobiol., Bd. 42. Leipzig, 1942.. 25. Husterit, Fr.: Die Struktur der Diatorneen und die 13edeutung des Elektronenmikroskops für ihre Analyse. 1, IL Arch. f. Ilydrobiol., Bd. 41 und 47. Stuttgart, 1945, 1952. 26. Ifustedl, Fr.: Die Diatomeenflora norddeutscher Seen mit besonderer Beritdcsiditigung des hohteinischen Seengebiets. Ebencla, Bd. 41 und 43. 1945, 1950. 27. Haslet*, Fr.: Die Diatoineenflora diluvialer Sedimente bel dem Dorfe Caj bei Konin im Warthegebiet. Sdiweiz. Zeitsehr. Hydre)., Bd. 11. Zurich, 1918. 28. Haste*, Fr.: Stil3wasser-Diatomeen ans dem Albert-Nationalpark in Belgisch-Kongo. Expl. du Pare Nat. Alb., lvliss. 11. Damas ()935-493M, Fast% 8. Briissel, 1949. 29. Iluslcclt, Das Studium der Testdiatomeen ais Einführung in die mikroskopische . Praxis. Mikrokosmos, Bd. 38. Stuttgart, 1949. 30. 11 uste(11, Fr.: Über clas Zeichnen von Diatomeen, I, II. Ehenda, Bd. 40 und 42. 1951, 1954. 31. II usteill, Fr.: Die Systematik der Diatorneen in ilion Beziehungen zur Geologic und ôkologie nebst einer Revision des lialobiensystems. Sv. Bot. Tidskr., Bd. 47, Uppsala, 1953. 32. 11 tistedl, okologie in Zirkelschlüssen. Arch. f. Hydrob., Bd. 51. Stuttgart, 1955. 33. 11 tiçtrilt, Zellteilungsfolge und Variabilitat Lei Diatoineen. Ach. f. Mikrobiol., Bd. 21. COI tingen, 1955. 34. llustrcil. Fr.: Die grundsiitzliche Struktur der Diatomeen-Membran und die taximornische Aus- wertung elektrtmenniikroskopischer Diatorneenaufnahmen. Botan. Not., vol. 108. Lund, 1955. iiirgensen, E.: Diatom Communities in some Danish Lakes and Ponds. Kong. Danske Vidensk. Sehk. Biol. Skrift., Bd , 5, Nr. 2. Kopenhagen, 1948. 36. Kolbe, R. IV.: Zut Okologic," Morphologie und Systematik der Bradcwassm-Diatomeen. Die • Kieselalgen des Sperenberger Sal7gebiets. Pllanzenforsch., herausgeg. von R. Kolkwitz, II. 7. • Jena, 1927, 37. Kew, R. W.: Crundlinien einer allgemeinen Ükologie der Diatomeen. Ergebn. d. 13iol., Bd. 8. Berlin, 1932. 38. Pete:wig, J. B.: The Aerial Algae of Iceland. Bot. of Icel.. vol. 2. Kopenhagen, 1928. 39. Petersen, J. B.: Studies on the Biology and of Soil Algae. Dansk Bot. Ark., Bd. 8. Kopenhagen, 1935. 40. 11.: Die Diatomeenflora der ostholsteinischen Fliel3gew5sser. Ardt. f. Hydrobiol., Bd. 44. Stuttgart, 1951. 41. Scheele, M.: Systematisch-Okologisdie Untersuchungen über die Diatomeenflora der Fulda. Ebenda, Bd. 48. 1952. 42. Scheele, M.: Die Lodikartenverfahren in Forschung und Dokumentation mit besonderer Berück- sichtigung der Biologic. Stuttgart, 1954. 43. Stint*, 11.-A. von: Entwiddungsgeschichtliche Untersuchungen an zentrischen Diatomeen. Arch. I. Nlikrobiol., Bd , IG. GOttingen, 1951. 44. Stosch, 11.-A. van: Die Oogamie von Biddulphia mobiliensis und die hisher bekannten Auxo- sporenbildungen bei den Centrales. Congr, Internat. Bolan., 8. Paris, 1955. . - .› • Translation of foreign titles:

[1] Contributions to the knowledge of fossorial Bacillaria in Hungary.

[2] Marine Diatomaceae of France and neighboring maritime districts.

[3] Atlas of known Diatomaceae, started by Adolf SCHMIDT, continued by M. SCHMIDT.

[4] Synopsis of Belgian Diatomaceae. 3 0 107.

[7] Fresh-water Diatomaceae of Germany.

[8] Bacillariophyta; in: Pascher, A., The fresh water flora.

[9[ The Diatomaceae of Germany, Austria and Switzerland, as well as of other European countries and adjacent maritime regions.

[10] Bacillariophytaf; in: Engler & Prantl, The natural families of plants.

[13] Diatom vegetation in Black Lake.. Flora and fauna on Funen ls^alnd,o . .

[16] Form changes among Pennatae.

[17] Numerous publications on auxospore formation, as well as nuclear and cell division, in The Austrian Journal of Botany, features complete bibliography on diatoms. G [18] Fast methods for the study of nuclei and chromosomes. [19] Diatom valves under the electron microscope.

[20] Investigations on the structures of diatoms.

[21] Collection and preparationof diatoms with a description of methods used for inspection and pteparation of cultures.

[22] Systematic and ecologica-l investigations of the Diatomaceae flora of Java, Bali and Sumatra, on material gathered during the German limno- 0 logical Sunda-expedition.

[23] Diatomaceae of the Abisko region in Swedish Lapland

[24] Fresh water Diatomaceae of the rTalay Archipelago [Indonesia], and the Hawaiian Islands.

oi [25] The structures of Diatomaceae and the role of the electron microscope in their analysis.

[26] The diatom flora of North German lakes, especially the Holstein lake region.

[27] The diatom flora in diluvial sediments found in the village Gaj, War- ta river district, Poland.

[28] Fresh water Diatomaceae of the Albert National Park in the Belgian 0 Congo. [29] The study of "test" diatoms as an introduction to mic-roscopy.

[30] The drawing of diatoms.

[31] Diatom systematics'in relation to geology and ecology, with a revision of the system for halobionts. _ 108.

[32] Faulty circles [circulus vitiosus] in ecology.

[33] Succession in cell division and variability of the Diatomaceae.

[34] The basic structure of the diatom Membrane and the taxonomical evaluation of electron microscopic diatom photographs.

[36] Ecology, morphology and systematics of brackish forms of the Diato- maceae. The Diatomaceae of the saline region of Sperenberg (Germany).

[37] Basic outline of a general ecology of the Diatomaceae.

[40] The diatom flora of East Holstein's s t,re ams

[41] Systematic-ecological investigations of the diatom flora in the Fulda river (Germany).

[42] Computer card systems in research and documentation, with special reference to biology.

[43] Investigations on the developmental history of the Centricae.

[44] Oogenesis in Biddulphia mobiliensis, and auxospore formation (as hitherto known) in the Centricae.

Legends for Plates 1-IV

The illustrations offer a limited overview of the multitude of forms that exists among the Diatomaceae and the pictures of their ap:.- pearance illustrate the character of a number of genera. The limited magnification (X200 to X500) does not always suffice for a clear View of the structural details. All photographs are made with the original

Leica camera.

1. Coscinodiscus 9. Eupodiscus

2. Craspedodiscus 10. Arachnoidiscus

3. Brightwellia 11,12. Actinoptychus

4. Aulacodiscus 13,14. Auliscus

5, Pyrgodiscus 15-17. Stictodiscus

6. Rattrayella 18,19. Actinocyclus

7. Cyclotella 20. Cosmiodiscus 8. 21. Pseudoauliscus 109.

uy 22. Hemidiscus 52. Campylodiscus

Rutilaria (valve view) 23. 53. Endictya 54. 24. Rutilaria (part of a chain) 55. (in 56 with especi- 25. Entogonia 56. Rhabdonema ally complex inter- stitial bands) 26. Huttoniella 57. Fragilariopsis 27. 58. Didymosphenia 28. H Yd rosera C 59. Epithemia 29. Hyalodiscus 60. Camyyoneis (valve without raphe) 30. Triceratium 0 61. Biddulphia (2 frustules shortly after cell division) 32. Kittonia 0 62. Amphicampa 33. Hemiaulus 63. Gomphopleura 34. Cheloniodiscus 64. Cymatopleura 35. 36.Porpeia 65. Plagiogramma

37. Cerataulus 66. Amphora (valve) ------38. Eunotiopsis 67. Frickea

39. Anthodiscus 0 ------68. Frustulia 40. Stictocyclus 69. Scoliopleura 0 41. Stephanodiscus 70. Scoliotropis 42. Glorioptychus 71. Oestrupia

0 43. Mammula 72. Caloneis

44. Asteromphalus 73. Cymatoneis 74 . 45. Rylandsia 75. Naviculae lyratae 46. Asterolampra 76. Naviculae punctatae 48.- Auricula 77. Naviculae nileolatae

49. Omphalopsis 78. Naviculae decussatae

50. Trinacria 79. Navicula tuscula 51. k 110, 80. Dictyoneis

81. Trachyneis

82. Neidium

83. Tropidoneis

84. Amphora (frustule)

85. Gyrosigma fl 86. Gyrosigma (structure)

87. Amphiprora (valve view, highest . focus)

88. Amphiprora (valve turned half way, edges of wings exceeding valve)

89. 90 Rhopalodia -.

91. Nitzschiae panduriformes

92. Nitzschiae lanceolatae

93. Nitzschiae tryblionellae

94. Triceratium (favus group); frustule wall under medium (94) and under 95. lowest (95) focus, cells closed at the inside by alveolar É- membrane, large circular opening on the outside.

96. Triceratium sendaiense; frustule wall under highest (96) and medium (97) G 97. focus, cells closed on the outside by alveolar membrane, small circular opening on the inside. The outside and in- side openings (94 and 97) are shining through.

Magnification in 94-97 approximately 1,500 : 1 0

Addendum re. p.78: p.64 For those who despite the time-consuming work still wish to select and arrange the individual diatoms themselves, or are forced to do so, I recommend the following methodical instructions:

HUSTEDT, F.: Vom Sammeln and PrMparieren der Kieselalgen sowie Angaben Uber Untersuchungs- und Kulturmethoden. (The collection and prepa- ration of diatoms with instructions on investigative methods and the preparation of cultures.)

ABDERHALDEN, E.: Handbuch der biologischen Arbeitsmethodik (Handbook of biological methods), Part XI/4 (1929 Reprinted (photographic method) by Verlag J. CRAME R, Weinheim an der Bergstrasse, Germany (West).

SCHMIDT, K.E.: Wie stellt man Diatomeen, Reihen- und KreisprMparate her? (How to prepare compound slides [series.and ciicles] of diatoms); Microkosmos 31, No.4 (1938). 111.

Plate I!

47i1;eke°'. 11 112.

Plate II.

il 113. Plate III



4. El

ri ••



Plate IV