A CONTRIBUTION TO THE MORPHOLOGY AND LIFE-HISTORY OF SARGASSUM TENERRIMUM J.Ag.' BY C. SURYA PRAKASA RAO, M,Sc. (Lecturer in Botany, Andhra University, Guntar, lndta) Received November 8, 1945) (Communicated by Prof Y. Bharadwajl, Ms-'., P'l D (Lond), r.L.S, r s l, F.A.S:.
INTRODUCTION NO contribution has yet been made towards the life-history of Indian Sargassums in spite of their relative abundance. The genus is one of the most conspicuous and common of the sea-weeds which one can see either washed ashore or growing attached to rocks below low-tide level along the east and west coasts of India. In 1848 J. Agardh described several species of Sarga~sum from this country (Specie~ Alga urn, Vol. 1, A:ga; F.tco/de; co,~,,p!,cte s, Land 1848) and in the following year R. K. G:eviile gave art account of fourtcen sp~'c,es ("Algm Orientalis--Desc'iption of new species belong;rig to th~ Ge:ms Sargassum.", Ann. and Mag. Nat. Hzst., S~r. 2. Vol. 3). B~rgesen (1933) also listed six of these species from Bombay in 1933 and one species from C~yIon in 1936. Th~,ywere: Sargassum tenerrimum J. Ag. (which h~ thinks syaony- mous with S. Campbellianum Greville), S. cinerum J. Ag. var. barberifolia Grun., S. Wightii (Grev. mscr.) J. Ag., S. ilici[olium (Ttlrn~ C. Ag., S. plagio- phyllum (Mort) J. Ag., S. myriocystum J. Ag., S. crist~,efolium C. Ag. Apart from a taxonomic description of Indian species of Sargassum, no attempt has been made to give a detailed account of any of them. At the suggesUon of Professor Y. Bharadwaja, the present work s was, therefore, undertaken by the writer to fill up this gap. HISTORICAL While a fair amount of anatomical and cytological work has been done on other members of the Fucales, very little is known about Sargassum. Miss S'mons (1906) studied the development of conceptacles and embryo in Sargassum filipendula, while Nienberg (1910) described the oogonium and
* From the Department of Botany, Benares Hindu University. 2 This is a portion of the work so~bmltted in part fulfilment for the M.Sc. Degreeof the Be.nares Hmdu Untversatyin 1939 B~ 39 40 C. Surya Prakasa Rao
sporeling development in Sargassum liaifolium. The later work is largely from Japanese workers of ~vhom Tahara (1909) and Kunzida (1928) contri- buted tte most. The former author records definite periodicity in the liberation of oogonia of Sargassum corresponding to that in Dictyota, while the l~tter gives a thorough account of the cytological details in the oogenesls and spermatogenests of Sargassum Horneri. The present paper, however. deals with Sargassum tenerrimum J. Ag.
MATERIAL AND METHODS The material for this investigation was collected from Bombay in January 1939.~ It was killed and fixed in formalin-acetic-alcohol. Other fixatives such as Land's formalin-alcohol, Dr. Lynds Jones' formalin-alcohol, and chromo-acetic solution were also tried and found useful on material collected lately by the writer from Vizagapatam. The usual paraffin method was followed in sectioning the material, sections being cut from 8-14/~ thick. Staining was done with Heidenhain's iron-alum ha~matoxylin and Delafield's ha~matoxylin. The latter, owing to its staining the young walls, proved more useful than the former.
MORPHOLOGY The plant under investigation agrees in taxonomic characters with the Sargassum tenerrimum described and figured by Boergesen (1933) and Setchell (1935). J. Agardh (1848) described the plant originally from the coast of Bombay under the present name, while Greville (1849) described the same as Sargassum Campbelliamum. Grunow (1916) later referred to this form as a variety of S. tennerimum under the name var. campbellianum. The plant has a-basal adhesive disc or hold-fast from which arises a short primary axis bearing several branches together. The axis is rounded, glabrous, scarcely 2 ram. across. The secondary branches fork repeatedly in their turn. "Leaves" are 2-6 cm. long and 89to 189cm. wide, gradually decreasing in size from the base upwards. They are thin, translucent and linear-lanceolate, with toothed margin" and rather indistinct midrib. Crypto- stomata are freely scattered on the "leaves" and receptacles whi!e they are rare on the axis. The receptacles are freely-branched structures being attached to the upper portion of tile stipe of the leaf. They are androgynous, spinose and show various cases of transformation of the branches., Cases have been observed where a portion of the receptacular branch may be a
t I am indebted to Captain S. C. Dtxat, M.^., u.sc., formerly of Wilson College, Bombay, or the supply of the material. Contribution to JCorpholo#y & Life.History o[ S. tenerrimum 41 leaf, or a bladder, or may be surmounted by a leafy expanse. The floats are either borne separately on short stalks or assoicated with the very much branched receptacle branches. They are spherical or egg-shaped, the tip b~ing commonly terminated by a small leafy appendage. T,~is description coincides more with that given by Boergesen than that by S~tcheU who describes under the same name a plant from Hong-Kong in which the "leav:s" are much smaller. ,~ATOMY S'mons (1906) summariscs the histological work done on the genus up to 1906. The work of Reinke (1876) on S. Boryanum, of O'.tmanns (1889) on S. linifolium and S. varians, of Hansteen (1892) on S. bacciferum, and the investigations of S mons herself on S. filipendula show that the growth of the axis and lateral organs takes place by means of a single 3-sided apical cell. In the ' stem' th-ee kinds of tissues are recognised :--:he assimilatory system, constituted by the epidermal cells; the storage system which is between the assimilatory and the innermost third system called the conducting system. According to Hansteen, the cells of the three systems are co1~unicating with each other by pores, but S mons (1906) could not see such pores in bet material of S. filipendula. In spite of b-~st ~fforts, the writer also could not see pores in S. tennerimum. In S. tennerimum also. both in the main axls and the laterals, there is a three-sided apical ceU which contributes along with its neighbourmg cells to the d,ffcrentiation of all subsequent systems. Tae apical cell (FLgs. I A and B) is situated in a pit or cavity which is its own creation, fo reed due to the quick succession in the production of cells in a tangentml plane and tt:e consequent lack of space for the elbowing of the resulting cells. It cuts eft cells parallel to the three sides and the base and thus maintains its ~dentlty throughout. The cells of the al3ove-mmtioned three systems get d~fferentiated at some distance from th~ apex. Th~ transverse section of the stem distmc~.!y shows the three regions, n. m2y, assimilato~y, storage and conducting. Tae outer- most assimilatory system consists of compactly-placed cells wim.h convex outer walls, covered by mucilage. Taey are rich in ch-ematophores and reserve material. Tae ceils of this system maintain their merist~matic activity throughout their life and always d,wde at right angles to the surface. They are also responsible for the development of male and fema!e concept- acles and cryptostomata. The cells of the second system, which also possess reserve material, are larger and possess wavy walls. They enclose many intercellular spaces. The cells of the conducting system are elongated, 42 C. Surya Prakasa Rao
]~t~. I A--transverse ann B---tongitudtnal section of growing point showing three-sided apical cell ; C-G--transverse secuons of receptacles showing mlhal stages m t!ze development of conceptacles C--showing conceptacle-~mtlal; D--showing two-celled stage; E--showing three-celled stage, F--showing five-celled stage, G--showing tongue-cell ; H-J--stages in the development of cryptostomata //--showing two-celled stage, l---showing five-celled stage, J--sho~mg tongue-cell of the same d~dmg Uansversely t, tongue.ce,ll, o, oogomum initial, m, rn'uellage. All • 1650. ContriSutzon 'o ,PlorpAolo#y & Li[e.H~story o/'S. tenerrimum r compactly arranged and possess oblique cross-waUs. They lack in reserve material. In a transverse section of the leaf also three regions can be recognized. The thickness of the leaf decreases as we pass from the m~drib to sides, this being due to the reduction in the number of layers of cells that compose the storage tissue. RECEPTACLES AND CONCEPTACLES Contrary to what we find in Fucus, the function of reproduction is relegated to specialized lateral branch systems. This character is also found in other Sargassaceous plants, such as Bifurcaria, Cystophyllum, Marginaria, Carpophyllum, etc. The receptacles are usually bisexual, although unisexual female receptacles are also met with. The conceptacles may be separated from one another by many layers of cells, or there may be only a little tissue between them. Their ostioles can be seen a bit raised over the general surface of the receptacle.
DEVELOPMENT OF MaLE AND FEMALE CONCEPTACLES The d~velopmental history of conceptacles given by Bower (1880) for six plants of Fucaceae, that the initial cell does not contribute to the forma- tion of the conceptacle, was supported by subsequent workers like Valiante (1883) (in Cystoseira), Oltmanns (1889) (in Halydris siliquosa, Himanthalia lorea and Ascophyllurn modosum), and Grauber (1896) (in Seiroccus~, till Simons (1906) in her account of Sargassumfilipendula contradicted this view. She was supported by Nienburg (1910). In early stages, the genesis of male and female conceptacles in S. tennerrimum is identical, so that a generahsed description will hold good for both. Each conceptaele owes its development to a single initial cell which earl be distinguished in the apical region of a receptacle by its possessing flask-shaped appearance, bigger size and larger nucleus and by getting more deeply stained than the surrounding cells. This cell may be one of those that have recently been cut off, or an old epidermal cell which regains functional activity. The lower part of the initial cell enlarges and is sur- rounded by storage cells, while the upper part is enclosed by the epidermal cells (Fig. 1 C). Later, a wall divides it into an upper cell, called by Simons the 'tongue-cell ', and a more or less bowl-shaped lower cell (Fig. I D). But, this wall in the present form is not so much depressed as figured by Simons (1906) (cf, P1. X, Fig. 2) in S. filipendula. Divisions are cofifined to the lower, cell only, giving rise to 3-celled (Fig. 1 E)stage before further dewlopinent occurs (Fig. 2, A-D). The ur~per cell persists as such till a 44 C. Surya Prakasa Rao
Fzo. 2. A--Lon~tudin~ ~tion of' fem~ concoptada showing transversely dJvidod oogo~ nium mlUai and tt,r l:crszstmg tonic-call ; B--Later stage showing &tmtcgratmg ~dk-c~s of oogonia ; C~stfl] later stage, shc'.~mg tongt.r Ferreting ; D--d~owing okla" oogcmia with vc~exvc food ; E--oogonium with crv~cvntJc apzcal dcprvs, ion ; F--pemphyscs from a matta~ female concepta~e, t, tongue-cell; s, stalk.cell; ,'n, meeoc~ton ; k, knob-hke swelllhg of paraphysl$ ; mu, mucilage..4 and C • 1650 ; B and D • 800 ; s • 300 ; F • 1330. Contribution lo Mor~holozy & Li#e.History of S. tenerrimum 45 very late stage. The lower cells divide longitudinally, expand lateraUy and form the wall of the conccptacle. In her paper on S. filipendula, Simons (1906) does not mention the exact stage at which the oogonium initials are laid down. But, in S. tennerimura they are laid down at a very early stage of the conceptacle (5 or 7-celled stage) (Fig. l, F). Usually two to four (rarely up to six) oogonium-initials arc laid down in each conceptaclc. The rest of the wall-cells contribute to the formation of paraphyses which are unbranched filaments possessing elongated cells, the terminal cell being knob-like or club-shaped (Fig. 2, F). The paraphyscs do not project beyond the ostiolc. The development of male conceptacle up to three or five-celled stage is similar, but further divisions are more rapid, giving rise to the cavity of the conceptacle lined by the potential antheridial mother cells. Hcrc the paraphyscs, unlike those of the oogonial conccptacles, are proliferations from the stalks of the antheridia. They may in some cases arise from the wall-cells also, but they are not multiccllular structures (Fig. 3, G and I-r). CRYPTOSTOMATA The development of the cryptostomata can also be traced to a single flask-shaped initial. Their early stages of development are similar to those of the male and female conccptaclcs. The tongue-cell, however, is generally sccn to develop into a flamentous structure (Fig. I, J) without undergoing disintegration as it does in the conceptaclcs. The cavity of a cryptostoma does not widen much. The paraphyses develop from wall-cells at a very early stage and grow throughout their life by means of a basal meristematic cell (Fig. 3, B, b), a type of bas'petal growth which is taken to be the sur- viving remnant of the original extensive ' trichothallic ' growth, so commonly seen at present in the lower members of the Brown Algm. The paraphyses in the mature cryptostomata project out freely (Fig. 3, ]3),and secrete mucilage The writer has observed oogonium initials in two cases of crypto- stomata of S. tennerrimum (Fig. 3, C) and this fact substantiates the view held by Bower (1880) and supported by other workers that the cryptostomata represent degenerate and non-functional conceptacles. OOGONIUM s As mentioned already, the oogonium initial is laid down very early in the development of the conceptacle (Fig. I, F). This cell divides into two
s The ~ oo~onium is retatn~l to denote oogonial co~tonts also a~ a matter of Conv~m~nce, though it does not directly function as tho female gamct~ as in other algae, but only after undor- going reduction divimon. 46 C. Surya Prakasa Rao
Fzo. 3. A--A female receptacle with the hberated oogoma attached to the coneeptacle by mean of mucilage-stalks, B--mature cryptostoma from a receptacle, m longitudinal section with projecting paraphyses, C--an exceptional case of cryptostoma showing oogonmm. D-I ; developmental stages ot Anthendlum. D--Anthenchal mother cells, one divided, transversely ; F~--Anther~dtal mother cell davlded into two ; F~later st,ago of E, showing uppor cell dlvldod transvexse, ly into stalk-cell and anthen&um proper ; G and H--mature antherldla with rosting ntw.~ a~cl unicellular paraphyscs ; /--mature anthorlchtun wath sperms ; J~an advan _c~l_ s ta~ge of embryo (reconstnacted) ; s, mucalag~.stalk ; b, basal n,mnstomatar c~ll ofparaphysis ; o, ooi~nium ; t, stalk-cell of anthendaum ; p, paxaphysls of anthezadtum ; sp, sierras. /l and J • 300 ; B • 800; G • 1330; therest • 1650. Con/rt$stion to MorpAology & Lt/e-H~story o/S. tenerrimum 47 cells of equal size (Fig. 2, A). The lower is caUed the stalk cell, and the upper one, after ~nlarging, forms the oogonium. At a later stage the stalk cell is usually seen oppressed between the wall-cells and the enlarging oogonium (Fig. 2, B). Thus, unhke Fucu$, the mature oogonium has no stalk cell. The, oogonmm enlarges and stores a lot of food material. Its nucleus, which also enlarges to some extent possesses a very prominent nucleolus and a little of chromatin material. The wall of the oogonium differentiates into ' exochiton ', ' mesochiton ' and 'endochiton '. Later, the exochiton ruptures irregularly and the mesochiton becomes mueilagenous and forms the stalk by which the detached oogonia subsequently attach themselves to the mother plant. The development of mucilage does not appear to be localised to form a gelatinous cap, but mucilage occurs more or less all round the oogonium, thus dtffering from the observations made by Kunieda (1928)in S. Hornert, by Delf (1935) in Bifurcaria brassiciformls and by Dawson (1941) in Cystoseira fieniculacea. In the mature oogonium there is generally an apical crescentic depression with raised edges (Fig. 2, E).
LIBERATION OF OOGONIA After the publication of Lloyd Williams' (1905) account of the periodi- city in the liberation of sexual cells of Dictyota dichotoma, there appeared a paper by Tahara (1909) describing a corresponding periodicity in the libera- tion of oogonia in Sargassum Horneri and S. enerve, the time of liberation being three days in the former and one day in the latter after full moon. In S. tennerimum also the similarity in the developmental stages of individual groups of attached oogonia and embryos at a particular region of a receptacle is suggestive of a corresponding periodicity in the liberation of female sexual cells. The actual mechanism involved in the liberation of oogonia is not well understood. Contraction of the tissues surrounding the eoneeptacle and the consequent gaping apart of the ostioles have been invoked as partial explanations (Farmer and Williams, 1898). Tahara (1913) has shown that in Sargassum tidal fluctuations influence extrusion of oogonia. Dell (1935), as reported by Dawson4) suggests that intensity and quality of illumination as well as hydrostatic pressure of the water are responsible for the extrusion of oogonia. Schreiber (1930) demonstrated in Fucus the liberation of oogonia by bringing about changes in turgor pressure of cells of conceptacle with the
* The observation of Delf refettod to by Dawson in the formcr's paper published in 1935 could not b9found by the writer. 4g C. Surya Prakas:~" Rao help of solutes. As Dawson (1940) puts it "various factors, internal and external, would combine to raise the pressure in the conceptacle and force the oospheres out via the already slippery ostiole". In her paper D~lf (1935) reports her observations on the nature of libe- ration of oospheres of Bifurcaria brasslcitormis and allied genera. After a careful study of several Fucaceous plants, she comes to the conclusion that the secondary attachment of oogonia by means of mucilagenous stalks formed by mesochiton are seen only in forms possessing unisexual conceptacles and this facilitates cross-fertilisation. But Dawson (1941) from a comparison of more than 30 members belonging to the Fucales refutes this statement, as mesochitonous stalks are met w~th in bisexual types also. Simons mentioned that the nucleus of the oogonium in S. filipendula directly functions as the nucleus of the egg. But the investigations of Nienburg (1910) on S. linifo/ium and that of Kunieda on S. Horneri have shown conclusively that three divisions take place in the oogonium leading to the formation of eight nuclei, of which seven degenerate, while the eighth one enlarges and functions as the gamete nucleus. There has been considerable d,fference of opinion regarding the stage at which the oogonia are liberated. Tahara (1913) states that the liberation of eggs takes place at the two-nucleate stage, this condition having been reached by the degeneration of six of the eighth nuclei. In a later paper Tahara and Sh matomai (1926) interpreted the binucleate condition of the oogonium as a result of the first division of the fertilized nucleus occurring simultaneously with the degeneration of the seven sister nuclei. Kunieda (1928) states that the nuclear divisions in S. Horneri take place while the oogonium is still attached to the conceptacle, In the Indian form, however, the writer has not been able to observe any case in which the nucleus of the oogonium underwent any division, while the latter was still attached to the wall of the conceptacle (Fig. 2 D). In the case of such oogonia as are secondarily attached to the conceptacle after having been released from the latter, eight nuclei were distinctly made out. Th"sobservation is in agreement with that of Oltmanns in a species of Sargassum, where he says that the nuclear division takes place after the liberation of the oogonia from the conceptacles. That all the eight nuclei of th~ oogonium are potential gametes is shown by the behaviour of oosph~res in S. ttornert, $. enerve (Tahara, 1913; Tahara and Sh~motomai, I926) and in S. tortile (Abe, 1938) where one peripheral nucleus may be fertilized in the presence of seven other equally vigorous gametes. Tahara (1927~ could induce parthenogenesis in several ~ontrt~utio, to Morp~blogy & Life.Histor~ of S. tenerrimum 49 oospheres in an oogonium. Abe 0938) noticed that oocas~onally two oospheres may be fertilized. The writer's observation of eight nuclei in the secondarily-attached oogonia also suggests that all the nucM retain poten- tialities for femlization and that the rest of the nuclei degenerate, when one nucleus gets fertihzzd. Thus, in the whole genus Sargassum, the oogonium should be taken to produce a single egg normally, although it contains eight potential oospheres. ANTHERIDIA The antheridia develop from the wall-ceils of the male conceptacle. A cell puts forth a papilla-hke projection into which large amount of proto- plasm passes. The papilla is then cut off by a basal wall (Fig. 3, D-I). The lower cell remains as the wall-cell of the conceptacle, while the upper one i.e., the papilla ceil, divides into two, the lower of these forming a stalk cell and the upper enlarging and functioning as the antheridium. The antheri- dium has a big nucleus with a prominent nucleolus and a little amount of ch-omatin material. Each is associated with generally one-coiled (rarely two-) paraphys:s developed from the antheridial stalk-cell (Fig. 3, (3). The mature antheridium (Fig. 3, I) has a thick mucilagenous wall. Cytological details have not been worked out. Kunieda 0928) gives the haploid chromosome number in S. Horneri as sixteen. He also mentions that sixty-four sperms are formed in each anthoridium and that each sperm is pear-shaped with two long cillia. In S. tenerrimum also sixty-four sperms have been observed (Fig. 3, I). It is interesting to note that even at a stage when we get yotmg sporelings attached to the receptacles we still find such anthoridia as have a pr:mlry resting nucleus, showing thereby that the receptacles are distinctly protogynous. EMBRYO Early stages in the development of embryo could not be observed. Mature embryos were met with plentifully. The sporeling which is found attached to the mother plant is spherical or ellipsoidal. The cells at one end are smaller than those at the other (Fig. 3, J), the former presumably giv.ng rise to rh'z)ids later on. There appears no relation to gravity in the forma- tion of rhizoidal cells. S~P,v 1. Th~ plant Sargamum tenerrimum J. Ag. has been studied. It is a moncceious spocics showing male and female conccptacles in de same receptacle. 2. Growth takes place by means of a single 3-sided apical cell. 50 C. Surya Prakasa Rao
3. The coneeptacles and cryptostomata have been traced to single flask-shaped initial cell. Tongue cell in conceptacles does. not divide trans- versely, but perishes after som~ time. 4. Oogonium initials are laid down at an early stage in the development of the conceptacle. 5. No mucilage cap is formed, as the mesochiton is uniformly thick all round. 6. The oogonium undergoes maturation-division only after the extrusion from the conceptacle. Only one egg is formed in an oogonium. 7. Ther~ is periodicity in the liberation of oogonia as indicated by the similarity in dovelopm-nt of attached oogonia and sporelings at a parti- cular region of the receptacle. 8. An antheridium produces sixty=four sperms. 9. Embryo produces small rhizoidal ceils at its on.= end. I0. Except for a few differences, the developmental history agrees with that worked out by S,mons in S. filipendula. In conclusion, I have much pleasure in expressing my indebtedness to Professor Y. Bharadwaja for his kind guidance and criticism throughout the course of the in,,estigation. REFERENCES Abe, K. "Uber dm Bofruchtung und lhre folgende erste Kerntellung bel Sargassum," Sol. Rep. Tohoku Umv., 1938, 13, 3, 253. (Cited from Dawson, 1940). Agardh, J. Species Algarum, Vol. I, "Alga, Fucoxdes comph~tens, Lund," 1848. (Cited from Boergcsen, 1933). Boergeaen, F. "Some Indian green and Brown Algae, especially from the shores of the Presidency of Bombay," Jour. Ind. Bet. See., 1933, 12, No. 1, 1-16. Boergesen, F. "Some Marine Algae from Ceylon," Ceylon Jour. Sct., 1936, S0c. A, Botany, 12, Part 2. Bower, F. O. "On the development of the conc~ptacle m the Fucaceae," Quart. J. mwr. ScL, 1880, 20, 36. (Cited from Simons'). Chamberlain, C. J. z'vtethods in plant histology. Umv. of Chicago Press, 1932. Dawson, A. E. E. "Studies m the Fucales of New Zealand. II. Observations on the female frond of Carpophyllum flexuosum (Esp.) Grey. •, Carpophyllum phyllamhu~ (Turn) Hook and Hare.," New PhytoL, 1940, 39, 3~ 283-302. "Some obom'vations on Cystoselra fetTiculacea (L.) Grey. Emt~ad. Sauvageau.," lb/d, 1941, 40, 4, 316--325. Dolt', E. M, (Mrs. Percy Smith) "Liberation of oogoma m BIfurcarta and other members of the Fucacear IbM. 19.~5, Contribxlion to Morphology & Lz[t.Hzstory orS. tenerrimum 51
Farmer, J. B. and Williams, J. L. "Contribution to our knowledge the Fucaceae, their Life- i~story and Cytology," Phil Trans. Roy. Soc. Lend. B, 1898, 190. (Cited from Simons', 1906). Grewlle, R. K. ' "Algae Orlentales," Ann. and Mag., Nat. Hist. Ser. 2, 1849, 3. (Cited from Boergesen, 1933). Gruaow, A. "A&htamenta ad cogmtionem Sargassorum," Verb. Zool..Bot. Ges Wlen, 1916, 66. (Cited from Boergesoa, 1933). Hansteen, B. "Studlen zur Anatomie und Physiologic der Fucoi dcen," Jahrb. Wlss. Bet 1892, 24, 317-360. (Cited from S1mons'). Hyot, W. D "Periodicity m the production of sexual cells in Dlctyota dwhotoma," Bet. Gaz., 1907, 43. Ku~leda, H "' On the development of sexual organs and embryogcny m Sargassum Hornen.," Jour. Coll. Agrtc. Tokyo, 1928, 9, 5, 383-395. Nienburg, W "Die Oogonentwicklung bcl Cystosewa und Sargassum," 1910. Flora, N. F. Bd. 1. Oltmanns, F Beitrage zur kenntniss der Fucaceen. CasseL 1889 (Cited from Slmons', 1906). Morphology und Bwlogie der Algen. 2rid ed. Bd. 2, 1922. Retake, J. "Bettragr zur Kenntniss der Tange," Jahrb, Wlss. Bet., 1876 10, 317-382 (Cited from SImons', 1906). Sehrelber, E. "Die Fruktifikatlonszelten und die Bedmgungen der Gamcte- nentleerung bei Fucus serratus," Z. Bet., 1930, 23, 273. Setchell, W A "Hong Kong Sea-weeds, IV, Sargassaceae." The Hong Kong Nat Supp.. 1935, 1-24. Simons, E. B "'A Morphological study of Sargassum [ilipendula," Bet. Gaz, 1906, 41, 161-180. Tahara, M. "On the periodical liberation of Oospheres m Sargassum,'" lbid, 1909, 23, 271, 151-153. "Oogonium hberatlon and embryogeny of some Fucaceous Algae," Jour. Coll. Set. Tokyo, 1913, 32. (Cited from Kunieda, 1928). "Experiments on the eggs of Sargassum," Bet. Mag. Tokyo. 1927, 41. (Cited from Kunieda, 1928). and Shimatomaz, N "Mitosen bci Sargassum," Science Reports of Tohoku Imp. Univ., 4th Series, 1926, Biology, 1. (Cited from Kunieda, 1928). Valiante, R. "Le Cystoseirae del Golfo di Napoli," Fauna und Flora Golfes Neapel, 1883, 7, 1-30 Williams, J. L. "Studies m the Dtctyotaceae," Ann Bet, 1905, 19. Yamanouchi, S. 9' M~t(X~lS m Fucus," Bet. Gaz., 1909, 47.