The Inheritance of Apospory in <Emphasis Type="Italic">

THE INHER,ITANCE OF APOSPOR,¥ IN SCOLOPENDRI UM V ULGARE

BY I. ANDEI~SSON-KOTT0 A~D A. E. C4AIICDNEI% Joh~t Innes Horticultu~'al Institution, Me,rton, Londo'Jb

(With Plates VI-XII and Two Folders)

TIt~ literature on apomixis and apospory is very extensive. Morpho- logical and taxonomic studies, and lately cytological and genetical work, have brought to light various important facts which have not only made possible extensive conclusions but have given rise to speculations in various directions. Among the more general questions which have arisen are those relating to the cause of apomixis and apospory, the relation of polyploidy to apomixis, the relation of polymorphism of plant genera to apomixis and apospory, or generally the part played by apomixis in evolution and species formation, and the alternation of generations. It is impossible here to go into the extensive literature on the subject, it will only be necessary to refer to the recent handbooks by l%osenberg (1930) and Schnarf (1929). It may be mentioned that, in addition to speculations on hybridism in itself as the cause of apomixis, whether on cytological (Winge, 1917) or comparative (Ernst, 1918) grounds, more definite views were expressed on t]zis subject by I~osenberg (1917), Whlkler (1920) and more especially by Hohngren (1919), and by l%osenberg in his later work (1930); these authors were conscious of the possibility of a genetic factor for tendency to apomixis, and have expressed themselves to this effect. More recently Schnarf (1929) expresses himself in the following way: "Die Anlage zur kpomixis diirfte in vielen Fgllen schon vet der Kreuzung vorhanden gewesen sein, and diese dr'trite eher eine ausl6sende als eine unmittelbar hervorrufende gewesen sein." (J-ustafsson (1932) is more definite and considers in more detail the possibilities of the origin of new forms and of apomi~s as a dominant or recessive character in triploid Yfaraxaca and Ar&ie,ra~ia. The frequent loss of Nnctional sexuality or the occurrence of apomixis following on apospory made investigation on the cause of these phenomena diflicult. An exception is found in the classical experiments of Ostenfeld (1910), with partly aposporoas and apomictie Hieracia. From 190 I~ff~erita~ce of Apospory i~ Soolopendrium vulgate t;he cross between I~he sexllal Hie,rc~ci't~'m, a,~,~'iculc~ and the partly aposporous and. apomictie H. a,~t~'anticte~t'm as d, a polymorl?hic F 1 generation was obtained, the c? parent probably being a heterozygoge. The 291 plants gave rise to true-breeding races or were sterile. More recently, genegical and cytological facts bearing directly on the cause and inheritance of asyndesis phenomena have been furnished by Beadle and M.cCOlintock :for Zea 2l/ia,ys in a preliminary note (1928) and f.urgher reports by Beadle (I.930, 1933). These aut;hors found a l~tlendelian recessive gene for failure of synapsis of t~he meiotic chromosomes. Gowen (1.928) has also given fa,ots which show that l~here is a recessive gene in D,rosophilct which causes aberrane meiotic chromosome beha.viour, and Blakeslee (1928) also mentions a recessive gene in Da,tu~'a which prevents pairing of the chromosomes at reduction.. The same attthor (1930) reports on a peculiar race, the only one in a considerable collec{fion Dom I-Iungary, conta,ining a recessive gene which in the homozygous condition causes a doubling of file chronmsomes. Apparently when the doubling oecm's early in mierosporogenesis, twin nuclei are formed. In. bo~h. single and twin nuclei further doubling may take place, producing nuclei which may contain as many as 96 chromosomes, gkstrand (1932) found a gene for asyndesis of t~wo pairs of chromosomes in Horcleit,'m, and Bergman (1.935 b) in Leo~,todo~'~,, and probably in Hie~'cteiu¢'*~. Several more instances have been found by various authors where h'regularities at meiosis are chromosomally determined. The two events, apospory and apomixis, are not always sufficiently distinguished by writers on problems appertaining to these subjects. This is partly due to the close proximity in the life cycle of the angiosperms of the spore stage, where meiosis usually occurs, and the sexual stage, i.e. development of the egg cell on the 9 side and the generative nucleus on the c? side. In ferns the two sta.ges, the spore stage where meiosis occurs and the sexual stage, viz. developmen~ of egg cells and. spermato- zoi.ds~ are widely separated and thus more amenable to investigation of the processes occm'ring at either stage, and[ of the possible relations between such processes. Anoi~her favourable situation in ferns is the possibility of ohtaining several sporophytes from one gametophyte. The terminology of the processes involved in gamel~ophyte formation without preceding meiosis, and sporophyte formation without preceding fertilisation or fusion of cells, is used differently by different authors. The nomenclature used by l:~osenberg (1930) is probably accepted by most botanists at the present time. In the present paper we shall use t~he terms as defined below: I. ANDE:RSSON-KOTT0 AND A. E. GA]:R,DNER, 191 Apomixis denotes the substitution for sexual propagation, of an asexual form of propagation, without fusion of nuclei or cells, in contra- distinction to amphimixis, viz. propagation by sexual fusion. Apomixis then inclndes the formation of a sporophyte from an egg cell without fertilisation (parthenogenesis), and ghe apomic~ic development of sporophytes from any other cell of the gametophyge (apogamy). Apospory denotes gametophyte formation from a somatic cell of the sporophyte (somatic apospory) or from a spore mother cell without preceding reduction (generative apospory, which occurs for example in Lastra, ea strata). Spore formation without reduction has also been termed apomeiosis (l~enner, ]9].6). Apomixis and apogamy should be separated from nucellar embryony and the formation of adventitious embryos, since in the former alternation of generations occurs, whereas the latter cases constitute methods of vegetative reproduction (similar to bulbil formation in ferns) without alternation of generations. In the present paper the term alternation of generations denotes the morphological Mternagion of gametophyte generation with sporophyte generation, as distinct from alternation of nuclear phases.

Mo])]~ OF CULTURE The aposporous Scolo~)e'n,(~'riu~n sporophytes in these experiments are of very striking appearance. They are therefore for convenience called "pemdiars" (shortened to Fee. or pees.). Both Knop agar and soil were used as culture media. The former method has been pre~5ously described by Andersson-Kott5 (1923, 1929). In the experiments here referred to, most of the hybrids were obtained by sowing the spores of the female parent (9 P.) on Knop agar in Petri dishes. Gametophytes of these were isolated, each one into a separate Knop agar Petri dish. The crossing of two gamebophytes is facilitated by the fact that antheridia occur early and archegonia later in the development of the gametophyte. When, after some time, the archegonia were developed and ripe, and it was ascertained that no angheridia were ])resent on the prothallium, the dish was filled with Knop's solution and the smaller d prothMlia, reared for the purpose in a,no~her Petri dish, were introduced and left for some hours in the solution round the _~ pro- thallimn. The solution was then poured away and the (? prothallia removed. The hybrids appeared after some ~ime and were subsequently transferred to soil. The same isolation method was employed for self- fer~ilisation of single galnetophytes. Each gametophyte in this case was 192 Inhe~'~;ta~ce of A2)osl)o~'y in Scolopendrium vulggre kept' on agar and t'here setf-fertilised, and t'he sporophyt'es subsequent,ly I~rallsferred t'o soil. Alt,ernat'ively t'he gamei~ophyt'es, aft'er having been iso]at,ed for some t'ime on agar, were t'ransferred to soil, each one ill a sel?a,ra.t,e l?Ot,, where it, ral?idly increased in size and WaR self-fert'ilised by adding wat,er t'roln above. When it' was desired t~o have descendant's from one l?rot,hallium bot,h t'hrough self-ferl~ilisat,ion and eross-fertilisa, t,ion, t'he prot,hallium in question wan isolat'ed, and when of good size was divided, and the parts again iso]atted. The l?art,s when established were used respectively :for self- and eross-fer~ilisat'ion. The eeehnique of separa, t,ion of 9 and d' pa,rbs on t,he aposporous out,growt'hs of t,he peeuliars, necessary when one wishes to secure d' part's for use in crosses, is dimeultt. This of course does no~ apply t'o t'he gamettophyt,es raised from spores, where t'he early ant'heridial st'age can easily be used an cL The aposporous out,growt,hs of the peenliars have t,herefore most,ly been used an -9- in ~he crosses wi~h normal, t,he hybrids being reeognisable from the beginning, from t,he fact' ttha,t, normal is dtominan~ over peculiar. The peeuliars occasionally obtained a~ t,he same t,ime can safely be assumed t,o have rem~lt'ed from self-fer~ailisat,ion, since peeuliars when selfed are known to give peculiars again. When gametophyt, es carrying peculiar (half t,he number of gamegophyt'es arising from Sl?ores from the F 1 from normal x peculiar or reciprocally) are used an d' in crosser wieh normal, it is advisable t,o wai~ until the next' generation to be sure of the hybrid nature of t,he sporophyttes obt'ained, since some normal sporophytes might accident,ally have been obtained from selfing of 6he normal prot,hallimn used an 9; these should breed true, while t,he hybrids should segrega~se for normal/peculiar. The Pet,ri dishes were kept moist' by ~he addition of Knop's solution, the soil by in51sion of water from below. Each pot' or dish was well covered wit'h glass, and the margin of error from eontt~minat'ion by stray spores or stray spermat,ozoids is negligible. The peeuliars are very t'ender and thrive only under glass bell-jars. l%el?eat,ed at,ttempts have been made go aeclimat,ise them to hot or cold greenhouse air, but without success. They may live for years under suitable conditions. No sign of a]?ogamy has been meg with. The normal l?lants in t,he experiments are in appearance fltlly normal and have been grown under the cultural conditions usual for Seolo- penal,flu,re. In t,he following discussion the term "normal" will be used t'o signify morphologically normal, whether het,erozygous for peculiar or not'. ~[. ANDERSSON-KOTT() AND A. E. GAII~DNEI~ 193

0I~IGIN OF THE :PECJULIAI~ STPOP~OPI:IYTE The peculiars arose from ~he spores of a normal sporophyte of the variety c~'ispum ,m,~l,ricatu,m, obtained from the collection of tile late Mr H. Si~ansfield, the origin being unknown. This norm-d crispum muri- ca,gum sporophyte was homozygous except for the peculiar character and to some exten~ for width of frond (Plate X, figs. 25, 26). When it was first obtained by me, gamegophyges from i~ were self-fertilised, fertilised in,ter se, and also crossed with o~her varieties of Scolopend'ri'wn'~ 'wdqare, and the results as to the iuheritance of morphological characters have been reported (1929). After the discovery of the peculiars among the descendants, experiments were started again for the elucidation of the inheritance of this character, the original c~'ispum muricalu'm sporophyte being still alive. Some results of a preliminary investigation of the peeuliars were mentioned in a paper of 19,31. The cytological da~a there given were based upon a snlall amount of material, of which the fixation was not satisfactory. A more thorough investigation was therefore started, the results of which are reported in the present paper.

D~SOI~IrTmN OF THE PEOULTAI~ SPOROPHYTES The peculiar type of sporophyte only attains a height of 8 cm., and may bear as many as twenty-five small fronds at one time, though it usually has less (Plate IX, figs. 21, 22, 23). The plants are thus con- siderably smaller than normal S. vulgate plants, and owing to their slender build would probably be overlooked in seed pans of commercial cultures. The proportions that the various parts of the peculiar sporophytes bear to one another are about the same as for normal sporophytes (apart from the aposporous outgrowths). This applies for instance to the size of the roots as compared with size of fronds, thickness of roots to Ieng~h of roots, and size of scales on the petiole ~o size of petiole. The development and arrangemellfi of the vascular system is the same as in the normal, though in the peculiar ie is of a more slender build. The fronds are pellucid green, or in the thicker types dark green, and are very brittle. The peculiars, though possessing most of the organs of a Ncolopend,riwm sporophyte, differ from the normal ,vulgate type and from all known varieties of this species in several respects. In the first place the fronds (see Plate VIII) never develop indusia, sori or sporangia. Secondly, there is, apart, from the vascular system, no differentiation of tissue in the leaf blade into spongy mesophyll and epidermis, as in the normals. All the 19zi Inheritance of Apospory i~ Scolopendrium vulggre cells are similar and straight-walled,, as in the gametophyte, except in old plants with large leaves, where occasionally a slight undulation of the walls may occur in cells situated near the base of the frond between t~he veins (Plate XI, fig. 31). There is no thickening of the outer walls, and intercellular spaces are very rare. Occasional stomata may be found. Fully grown fronds are several layers thick, except at the edge (Plates VI, VIII). The leaf blade thus consists, apart from the veins, of prothMliM tissue only, and this applies not merely to the edge but also to the area between the veins and ~he base. The fronds of the peculiars are fitrther- more characterised by their obligatory habit of developing their gametophytic tissue into prothallia (]?late VII). The whole edge (or ]?arts of it, but not as a rule separate cells) gradually grows out into a prothalliM sheet at,tached to the frond, ghizoids (Plate VII), archegonia and antheridia appear on the outgrowth, the frond is then weighted down by the gamete- physic outgrowth until the latter: reaches the soil and establishes itself. After some time the stalk of the frond and the lamina rot away and the gametophyte is independent. The new gamctophyge aposporously developed in t;his way possesses normal arohegouia and anCheridia froln which after fertilisation similar peculiar sporophytes arise. Up to a certain stage the development of the fronds of the peculiars follows the same lines as that of the normM types of S. vv,lga~'e. Thus the first smMl frond as a rule h as a single bifurcation of the vein (Plate V}, figs. 1, 2). Successive fronds with greater expansion in width and length develop nmre branches of the veins, from the more or less fa,n-shaped type (Plate VI, fig. 4) to types with a more and more developed central vein (Plates Vt, fig. 3, VII, VIII), h'om which the primary veins with their bifurcations appea,r. In the peculiar: sporophytes with the best developed fronds the primary veins bifurcat.e twice, the primary veins a,nd their branches extending l?arMlel with one a.nother Cowards the margin, as in normal N. vuh/a.~'etype (Plate X, fig. 28). The veins are free. The development of venation, as in the vulga.~'e type and the normal varieties, is int, imately connected with the development in size and shape of the frond. The shape of the fronds of mature plants varies to some extent. Most of the peeuliars have a compa~ra.t,ively short and broad lamina with the prothallial lobes projsct;ing in an untidy way, or forming a eont, inuous frilly prothMlium all round the h'ond (Plates IX, VII). As t,he fronds grow out they usually become deflexed. A few instances of pronouncedly differen~ shapes of t¥ouds hays occurred: (1) One prothallium when self-fertilised gave all peeuliars with I. AN])EgSSON-I{OU:T6 ANJ) A. N. G~m)NE~, 196 ma,tm:e fronds of more or less circular outline and fan-like venation (Plate VIII, fig. ]8). A very striking feature here was the long narrow claw-like lobes, each of' which grew out into a prothallinm, the main growing point of which was situated a good. distance froln the vein ending but in a continuous line with it. The same eype of frond, wil~,h each vein ending in a claw-like prot~hallus lobe, but5 with a pronounced mid-vein instead of the fan-like venation, occurred in another family. (2) Another prothallium in family 10/24 on self-fergilisation gave peculiars all with comparatively long and broad fronds, with a well-developed mid-vein (Plate VIII, fig. 15). The basal pard was broad, with projecting lobes and contained a strengthened vein in the manner of the normal sporophytes of the vat. sc~gittahm~ 1)~'qject'~mz (Plate X, fig. 27). The primary veins were twice or more fro'care. The edge was finely frilled, on account of ghe fact, that the prothallial outgrowths were just beginning to develop. The apex was often furcated. (3) A peculiar, the result of gametophytes in family 1.0/24 fertilised i~zte~' se, had. exceptionally long and narrow fronds, a broad base and. narrow uneven projections here and there along the edge (Plate VIII, fig. 16). The thick, dark green fi'onds were thinner towards the edge, where a single layer of gametophytie tissue made a narrow transparent margin. The whole edge grew out into a continuous prothallium. The fronds were rolled back and very brittle. (4) In another family the peculiars were s pecia]ly well developed, with. comparatively narrow fronds, bright green, of good substance, the apex furcated or branched and the mid-vein well developed (Plate VIII, fig. 17). In no instance (among several hundred plants) has a pecnliar had ~he ~;?,dgc~'e type of long stra, p-shaped frond, or the shape characteristic of e,ris'j)~L~, ,m,~,~'iea,t~m~. The hen,rest approach was perhaps found in the form described under (8), which differed, however, in its broad base. It, is possible that ghe plants under (2) above, and also the type figured on Pla,f,e VIII, fig. 14, correspond in. lead sha,pe to gh.e vat. sc@Zta, t~t,,m p~'qject~t,~, (Plate X, fig. 27), which was one of the parents, the other parent being the original sporophyte of the vat. e~'.~:sp~'m, ~'~o',iec~t,~.m~; and l;hat the more untidy looking types with a cordate base correspond to the v~dyc~'re type or c'Hsl)~m, ~m~',icat~.m~. shape. This would be supported by the fact that all the peculiars from var. c~'isl)~,~ ,m~,r.ieat~m~, when its gametophytes are fertilised i,~zte~" sc or selfed, are of the latter type. The peculiars described ,nder (~1:) came from a normal sporophyte with furcated apex. Mm'ieation of the upper surface, a character for which the vat. c~'is2)~m~ 'm,to"ic(ttv,~ was homozygous, is more or less definite in some Journ. of C4enegies xxx:~ 13 196 I~gl~e'J'itc~zce of Apo82)o)'y'i~, Seolopendrium vulgare peculiars, while in others it is clearly absent, as expected in the different families. Other families are less clear-cut in this respect. The aposporous (prothallial) outgrowth is never nmrioated.

INI'IEI{ITANCE O]r TIIE PEGULIAR, CNAP~ACTEI{ The data, of Tables I and II show that the peculiar character is due to a single recessive factor. G ametophybes from the original heterozygote (viz. our ]?aa%icular sporophyte of the vat. e~'isl)'em~ ,m,'tt,~'iec~,t,wm) were selfed and fertilised i~zte,r se. Similarly the gametophytes from the hybrid betsween c,r,i{~),~,'~,t,m,,u,q'iec~t,~,'~, (<~) and a, certain sporophyte of the var. scc.gitlcma,~, p,r@ct,wm, (9) were selfed and fertilised i'~te'r se, ~md some of the gametophytes from this hybrid were crossed (as -9- and d) with a ~rue-breediug wdga~'e type. The results of random mating a,mong prothallia from the same individual are given in Table I, those from selfing prothallia in Table II. Of the fifty tested gametophytes from 10/2~t, fourteen were derived from fourteen of the 64 spores of a single sporangium. Of these five gave normal and nine peculiar sporophytes. Among the normal sporophytes derived from random mating of prothallia from heterozygotes, fifteen were tested, of which seven were homozygous don~inants and eight were heterozygotes. In the family from one of these heterozygotes (15/30) three plants proved to be heterozygous and one was homozygous. From heterozygotes, the prothallia which gave peculiars when selfed gave normals in all cases on crossing (as 9) with homozygous wdgc~,~'e type. (Twenty prothallia were tried.) The segregation from some of these is shown in the table. Prothallia which when selfed gave normals, gave on crossing with wdga,,re type only normals (eleven prothallia tried) which subsequently bred true. When gametophytes were used as c? in crosses with vt@a~'e type, heterozygotes and homozygotes were similarly obtained. Three of the former and four of the latter were tested. Peculiars when selfed have given several hundred peculiars again, and no normals. As shown in the tables, the close agreement with Mendelian expectation leaves no doubt that a single factor is concerned. It~ view of the flint that no cross-overs have occurred there is no reason to assume that peculiar is carried by two or more linked genes. Beciprocal crosses behave in a similar way. The lt'1 and Nrther gener~- tions of urn:reals have spores well developed, and good germilmtion occurs. It is remarka,ble dm,t all peculiars have the same history in respect of general development, apospory, absence of sori, spora, ngia and spores, I. ANDEgSSON-KOT~0 na'~D A. E. GAIRDNER 197 a single factor being responsible for this, a,t~d allelomorphie to full normal deve/opment.

TABLE I P,rofleny of hete.rozy,qotes, ,qametophytes.fertili,~ed, int;er se ]Jal'enI) Sl)Orophyte Origin of' p~rent Normals ]?eeuliars

crisl)Um --- 90 29 'muricatum 15/30 f G~me~ophytes ofe,rispum muricat,um £ertillsed 147 50 16/30 "~ inter sc 139 4.1 10/24 sagillalum l)rojectum ~ x crls2)um ,mu,ricat,wn~ c2 269 94 18/30 C~a.nletophy~es of 10/24 ferl,ilised inter se 107 43 20/30 ,, 151 44 300/29 ,, 103 30 301/29 ,, 117 34 133/29 ,, 102 30 19/30 ,, 99 39 53~/31 One gametophyte of 10/24 (giving 1)eeuliar 153 60 when selfed) as ~- × vulgate type ¢ 536/31 Ano~hm' dR~o 199 73 ~74/31 Another di~to, g~ve 2 sporophytes 164 52 139]32 -- 131 40 165/30 vldgr~re tyl)e ~ x t0/24 62 22 TotM 2033 681 Expectation 2035-5 678.5

TABLE II Pro qeny o/' heteroz.!lgotes, gametoph?/les self:fertili.~ed

]?ra'eng ]?hytes sporophyte Origh~ of parent Normals Peeuliars dead cr ispum -- 19 20 4 'm,~trical.z~n, 10/24 sagittalum prqjecl,.u.nt 9 x cri.spum muri. 23 2,7 9

536/31 Gametophyte of 10/24: (giving peetKiar 5 6 -- ~4en selfed) as 9, x wd.qctre type c~ 65/30 wdg~rc l)ype ~ x 10/2'.4 d' 9 I0 -- Toi~l 56 63 -- Expeet;~timl 59'5 59"5 --

INHERITANCE OF GHARACTEI~S OTHE/~ THAN PECULi[AI¢ Several other characters segregated along wRh peculiar, Murication is domimmt over its absence (Andersson-KottS, 1929). 0l~r original sporophyte of the varieb~ c~iSl)'Um ,mu,~'icat~tm was ]lomozygous for this character. Among its progeny the sporophytes heterozygoas for peculiar were less m~wie~ted than the homozygous normals. In the peculiars mugcation is dig%stir to score, owing to the simple development of the lamina, and R can only be scored in Nlly grown plants. The plant 10/26 13-2 198 Inheritance of Apospory i~7, Scolopendrium vulg~re (the hybrid between sa,gittatu'm l)rqjectu'm, and cr,isl)u,m muricat,u,m,) was het,erozygous :for peculiar and murieation, both. these fact,ors having been derived from f,he c'ris?)v,m mu,ricatu,m parent,, Fifty ga, met,ophyt,es were selfed. Of these twenty-three gave normals a,nd ~wenty-seven gave peeuliars. Out of the nineteen normals which were kepl; to t,he :Nlly grown stage ten were nmricated a,nd nine nola-muricated. Ten of t,he peculiars were kept, five of which were murieated and five non-murieat,ed. T])e t,wo fact,ors are clearly not, linked, The factors Nr leaf shape influencing the development of lateral, apical and basal lobes did not segregate clearly in families including peeuliars. Though some extreme t,ypes of leaf shape were found in ~he l?eeu]iars, their classification was not possible.

SUCCESSIVE GZENEP~ATIONS 0]?' THE PECULIAP~S Before going on t,o describe the chromosome numbers for norulals and peeuliars ill these experiments it lna,y be lnentioned that the c]lromo- some number for wild S. vul.qare fl'om various localities and of all varieties investigat,ed by us has been 60 for sporophytes and 30 for gametophytes ~. No irregularit,ies in ehrolnosonm re|tuber corresponding to those to be described below have been met with elsewhere. The material was fixed in Flelmning's solution and the number of ehronlosolnes determined from side view of lnetaphase plates, the phase most favourable for counting. It is possible that the basic chrolnosome nmnber for ,~. vulqa.re is 15 and not 30 (see p, 217). As st,ated above, the peculiars selfed or crossed with peeuliars give in successive genera,tions peeuliars again. Since obligatory apospory is not here followed by apogamy, the chromosome number ought to double in each successive generation of sporophytes. This expectation is not, always fulfilled. The chromosolne numbers for t~he two families most extensively investiga,i, ed are given in Pedigree II for the family A (froln the original S. v. crispum muricatu,m) and in Pedigrees IV a.nd ¥ for the family B (fl'om saqittctt,tt, m p,rq~ectu,m, ~_ x c'rispu'm 'm,uricatu'm, c~) (bot,h referred ~o above). Scheme I shows the chromosome numbers for different, generations in a schen]at,ie way. Though in many instances the chromosome number ea,n be given definit,ely, in other eases it is only approximate. When a definite number is given, e.g. 45, 50, 55 or 60, these nmnbers were found, but, owing t,o 1 A haploid number of 32 wa.s found by St;eVellS(1898), Gregory (1904) and Farmer and Digby (1907). For the apog~mmus and aposporous variety erisl)~.v~, f2r~v~,mo~dac Farmer and Digby gave tbr embryos 80, 95-1(/0, in 1)roi;hailia 70, in archcgonia 80-83, and in angheridia 70-82. I. AND:EI~SSON KOTT0 AND A. _E. GA]:P~DNE:g 199 ghe crowded condition of 6he chromosomes on the metaphase ]?late a smM1 margin of error shonId be allowed for these numbers also. Nmnbers given as ~I5-50, 50-55 and 55-60 could not be established[ with accuracy, but lay within the range given. The same applies to the higher chromosome nmnbers, though here the accuracy may be less. To sumrnarise for both families: (i) Parent, sporophytes and F 1 have 60 chromosomes. The G1 generation all have 30 chromosomes (established from 20 gametophytes, some of which were bred from; see pedigree charts). The chromosome nmuber of the F, peculiars ranges from 45 to 60. p var. 8a.(lillal~tnt ln'ojccDHn 9 × var. crispum, muric~daut c~:~ ? 60 G 30 31) it) 60 F~ 24

(I~2_ 30

F~-]" 45 45-50 50 50-55 55 55-(10 60 I t I i I I I (l,, /,,45 /"\45-50 /\,50 /\50-55 55 /\55MJ0 /\ 60 Fa-I' 70 tx) 90 85-90 1,o 9'5-100 70-75 1~o 100 76-90 to 91)-100 85 to 100 80 t~o 100-115 [ I G:I 70 l,o 90 70-75 1;o 100 \\ (7O/ ",~5-s0) s0~-85)

F a 95-105 95-110 96 tO 100-t02 * Ill family A var. cr~s]ntm m~tricat~m was trea,ted as an F~. "]" The chromosome numbers of family A ~re ino[uded in f, hose numbers. Scheme I. Chromosome numbers of/-/'~-A,i peculiars in families A and ]3. The F 3 peculiars obtMned from selfing the F 2 peculiars with 45 chromosomes, have chromosome numbers ranging from 70 ~o 90. The F 3 from F s with 45-50 chromosomes have 85-90 to 95-100 chromosomes. The F s from F~ with 50 chromosomes have 70-75 to 100. Those from 50-55 have 76-90 Co 90-100. Those from 55-60 have 85-100 chromosomes, and finMly the f a peculiars from the F 2 peculiars with 60 chromosomes have 80 to 100-115 chromosomes. In F,t only five sporophy~es have been counted, none of them possess ghe full chromosome number (viz. double the parengal chromosome number). (ii) The chromosome number ira F= is in no instance below ~15, which equals the number of ~he preceding gametophyt~e (30) plus half this number (15). In Fa, Mthough the g5-chromosome F 2 gave about 70 chromosomes in Fa, this increase is not always exactly equal to one and 200 Jnhe~"itance of Al~o81~o'ry in Seolopendrium vulgate a half times the number of the preceding generation. There is thus a progressive decline in l;he rate of increase as the numbers in the parent sporophyte become larger. From the /Y2 sporophytes with 45 chromosomes the l~;s numbers range from 70 to the double munber 90, from f,he F s with 60 chromosomes the number may be as low as 80 and fihe double number is never attained. Again from//'3 with 80-85 chromosomes the double number (160-170) was not obtained. (ill) It is a remarkable fact that the gl galuetophytes when selfed give as a rule sporophytes with varying chromosome numbers. So far only one gametophyte, in family A, produced sporophytcs all with the same mlmber, i.e. six sporophytes from (4~ no. 28 had 60 chromosomes. Similarly none of the l~ peculiars has given sporophytes all with the same number of chromosomes, when several sporophytes were obtained fl'om one gametophyte. (iv) The same results are given by the #d1 gametophytes fertilised inter' se. (v) The ehrolnosome number of peculiar sporophytes is the same throughout the plant, from the first roots and buds to roots of bhe old plant. The same number is also found in the aposporous outgrowth, which is here the gametophyte generation, Furthermore, the different embryos have been found to vary in clhromosome number, like the sporophytes.

SUCCESSIVE GENEI~&TIONS OF NOI~h~ALS The normals in the two families, _& and B, just described show the same variation of chromosome number of the sporophytes in F2, when single gametophytes are self-fertilised (see Scheme II). ~kllthe ~/I gamcto-

G~ 30

l~ norm~ls ,15 45-50 50 50-55 55 55~i0 6(I \ -y ] G. 30 I 1,~ 45 to 6o I I (]~ 30 3o Scheme I.[. Chromosome numbers of normal,~ in ih,milies A am[ .B. phytes with the one exception, mentioned on p. 201, have 30 chromosomes (15 counted). The Fo sporophytes derived from them have 45-60 chromosomes like the peculiars. They are fnlly fertile, all spores being well developed and germinating well. The (~,, gametophytes investigated, I. ANDER, SSON-KOTT0 AND A. ]~. OAIR,DNEI~ 201 whether obtained :5:ore the F~ sporophyf,es with ,15, 60 or a,ny intermediate mtmber of chromosomes, all (except four) had 30 chrolnOSOlUes (a fact established fl'om seventy-four G2 g~metophytes, seine of which were subsequently bred from, see Pedigrees I and III). These again upon self-fertilisa.gion gave an _F.~ generation of norlna[s with ,t.-5-60 chromo- seines. Moreover, it is evident that ca.oh G~ gametophyte here also gives sporophytes with different numbers. The numbers of sporoph.ytes from each G2 gametophyte are not as large as ~hose from each (Yl gametophyte, bug both 4:5 and 55-60 have been obtained :from the sa,me (Y2 gamegophyge and also ~[5 and 60, 50-55 and 60 from otlhers; and one gametophyte gn,ve sporophytes with ,15-50, 55 and 55-60 ehromoso~ues. One (~,, ga,me- tophyte gave only 60's (:four sporophyl, es). The chromosome numbers in F~ are seen to vary, whether the sporophytes are derived fl'oln 4:5, 50 or 60 ehromosolne F2 sporophytes. There is ~hus a similarity in behaviour between the peeuliars and the aormals, inasmuch as bo~h F~ and F a in both ca,sos are apt to ha,re a lower chromosome number than would be expected. Another silAlarity between normals and peeuliars is that probably each (~1 gametophyte gives sporophytes with a range of chromosome numbers. In ~he normals, moreover, it is remarkable tha~ all ~he Go gametophyf,es (with the exception of those mentioned on p. 202) have .30 chromosomes. NormM sporophytes from fertilisation of G~ i~,te'~" se, both homozygous normals and those he~erozygous for peculiar, behave in a similar way. Neither the original c,risy)z~m mzL~'icc~tzt,,m sporophyte nor any of the normal F t or Fo (homozygous or heterozygous) sporophytes have shown any gross disturbance Ms reduction.

THE 0CCUP~I%ENCE OF SPOI~ES WITH MOI~E THAN THE HAPLOID CHI~OMO- SOME NUMBER, AS INFEEI~ED FI%0M THE GAMETOPItYTIC CHI~OMOSOME NUMBER With the exception of six or seven gamet;ophytes, all norma.l galnetophytes in all generations and also the G 1 giving peculiar have 30 chromo- seines. Fewer than 30 chromosomes have not been found in gametophytie tissue. It may then be inferred ~hat the spores as a rule have 30 chromo- seines. The exceptional (six or seven) galnetophytes had more ~han 30 chromosomes. These a.ll occurred in the family fl'om c~'isl)v,,m ,mv..ricatu/m, (family A, see Pedigree I), and all gave normal sporophytes. Only one occurred in ~71, the rest in G2. (i) In G1, the one gametophy~e (no. 1) with more than 30 chromosomes had 4:5-50 chromosomes, while fourteen had the expected 30; 202 l~he'ritance of A2)ospory, i~ Seolopendrium vulgate crispum m u,ricatum itself having 60 chromosomes. The 4:5-50 galneto- phyte (no. 1) gave upon selfing twelve normal sporophytes, two of which were ascertained to have respectively 90 and 85-90 chromosomes. (ii) Of the G~ gametophytes, one (no. 8) was derived from G~ no. 4: (30 chromosomes) selfed,/~'~ sporophyl~e 200/30 (~5 chromosomes). The chromosome mtmber for this gametophyte (no. 8) WaS no~ obtained, but it gave on selfing two sporophytes with 85-90 chromosomes, while sister gametophytes gave ~he usual range. The same G1 gametophyte no. 4 (which in 1~, gives the usual range in chromosome nulnber) gave from another/~'2 sporophyte, 75/30, besides nine G~ with 30 chrolnosomes, ~wo gametol?hytes with respectively 55-60 and 50-55 chromosomes. The latter gave two sporophytes with respectively 80 and 75-80 chromosomes. One G~ derived from G1 no. 6 selfed,/~2 506/31 (55-60 chromosomes) gave, besides aine G~ with 30, one the nulnber of which was not obtained but which must have had lucre, since it gave on selfing one sporophyte with 80-85 chromosomes. Furthermore, one F 2 normal sporophyte obtained from G~ fertilised i~tcr se had ~f5 chromosomes and probably gave one or two gametophytes with more than 30 chromosomes, besides those with 30 chromosomes, since in/~3 from i'ertilisation inter sea sporophyte had 80-85 chromosomes. As seen in the pedigree charts, the percentage of spores with a higher chromosome number than 30 is very low. It is still lower if the number of gametophytes which have been ascertained to have 30 chromosomes, but which were not bred (and hence not included in the charts), are taken into account (viz. altogether 109 gamegophytes).

ON THE PEI~CdENTAGE OF SPOI~OPHYTES ~VITK FULL CtlI:tO~OSOME ~'IUMBEI~ Since the chromosome number throughout a plant is the same, and apogamy does not occur, the mm~ber of chromosomes in the sporophyte should be the sum of the nmnbers of the parent gametes. It is also evident from extensive data that the gametophytes from norml:~ls always have 30 chromosomes, a.nd that the chromosome number in the peculiars does not alter in the transition from sporophyte eo gametophyte. Hence various conclusions may be drawn from t,he chromosome nnmbers of the sporophytes obtained by selfing ganaetophytes, fert,ilising them inter se and crossing them reciprocally witch v'ul.gare type. I. AN1)E~%SSON-KOTT0 AND A. E. GA~-~DN]~]~ 203 In ~hc following all ra~ios are: less ~han the full chromosome number :Nll chromosome number. The former includes, in normals of all generations and in/~,'s of peculiars, TABLE III No. of SpOl'ophyt;es wigh 2, L£m l~han full ~ull ~ ehronlosonlo ehl:onlosonte 110, ]lO, Family A JQ. normals from Gt selfed 24. 5 .lQ. pees. from G1 selfed 8 9 F. normals from G1 i~tcr se 7 1 F, pees. from d I i.~dcr se F~ normals,from 6'1-G. seized 33 12 .F~ pees. from #l-Cla seized 8 1 Fa normals fl'om (71 inter ss-G= i~ds'r se 8 3 .F,~ poem. from (/1-Ga-Ga seized 3 0 l~a,mily :B Y. normals fl'om G~ sellbd 27 7 .F2 pees. from G1 selfed 37 i0 .l~'. norman from 6'I '/n/or sc 19 2 1~ t)ees, from (41 in, let se l~t I 1~'a normals from G1-G.. seiZed 19 3 Y~ pees. fl'om G1-Q. setfed ]2 7 (if'ore B-P) from (41 inter ~'e-(le seized 21 16 Total of lP:~ pets. 33 23 l~':~ normMm fl'om dl i~dcr so-d4, inter me 3 3 F~l pees. from (~1 inter sc-G.-Ga seized 2 0 No. of Pereengage of sporophy~es sporophy~es wigh wi~h A__ t Less Less t,lum t'uH l~'ull bhan full l?ull eiu'omo- elu'omo- ebx'omo- eln'omo- seine seine 8olne mollie 11o, 11o, no, 11o, gesull~s from .Families A and :B togel~her le.. normt~ls from (41 seized 51 12 80.5 19.5 l/'a peos. from 6'~ molfed 45 19 70.3 29.7 #',, norm~ls from G1 inter se 26 3 89.7 10.3 l~'~ peon. from G1 inlet se [d: 1 93.3 6.7 /~:~ normals from G1-U," seized 52 25 67.5 32,5 .F~ pces. from (41-G." melfed ~1 24 63.1 36.9 F u normals from G1 i~dcr me-G,, bdcr sc 11 6 64,7 35.3 .F l peem. from (41 selfed and Jilter se, (4s-(7 a selfed 5 0 -- -- 1"~ tall normals (from melllng and inlet me) 77 [5 71.4 28.6 F~ all pets. (from selfing a.nd inter ,~c) 59 20 75.9 24. I F a all normals (from selfing anti inter me) 63 31 67.0 33.0 all chromosome numbers from ~15 go 60 including 55-60, but excluding 60; the la,t~er (full chromosome number) contains only the 60 class. This arbitrary division is more convenient thau if one includes ghe 55-60's in the full-nulnbcred ctass, and ~he results are not appreciably d if/erent. 204: Inheritance of Apospo'ry i~, Scolopendrimn vulgare For Fa-G a sj?orophytes of the ])eculiars tile full chromosome number is double/he chromosome number of bhe .F~-G~ peculiar from which ib was derived. The number of ]?]ants wibh less than and also with bhe full chrom.o- some number for the generations in. families A (derived from c'rislm,,m ,,m,~'icatu'm,) and B (from sa,gittal, u,m l~,roject'wm x c'risl)'wm, "m,u'ricc~.t~e,,) are set, out in Table III. For more detailed breeding of bhe families from selfing, reference may be made to the pedigree charts. It appears from the tabJe that: (i) If fa,milies A and B are taken ~ogethm' every rztio, in normals and peculiars, obtained both from selling and fertilisation inter se, in a,lJ generatimls, she ws less of the fuji-numbered category than of the category eonbaining sporophytes with less than the double chromosome number. If the daba of the two :fa,milies are taken separa~,ely, the only place where there is a higher number of :full-numbered than of less-than-kdl mlmbered sporophybes is in Gmily A, F 2 peeuliars from selfing, but the difference between this ratio and the other ratios for F 2 from selfing is only on bhe borderline of significance. The F 3 normals from fertilisation inter se in. family B were only 6 (3 : 3) which is too low a figure to be significant. (ii) Comparing bhe F~ ratios in. normals with those in peculiars for both Gmilies togebher, bhere is no signifieanb difference between the rabies in the normals and in the pemdiars, whether obtained from selfing or ferdlisation i.nte.r se, or both together. In Fa, however (comparable numbers only from selfing), there are more sporophytes with the full chromosome nmnber in the peeuliars than in the normals. (iii) Comparing sporophytes obtained from selfing of gametophytes with those from ferbilisation inter se, for the different generations separately and separately in f~milies A and ]3, the only ratio showing a barely significant difference is found in bhe F~ peculiars from selfing as compared with fertilisation ,inte.r se. Taking the two families bogether, the ratios obtained from selfing show no difference of statistical imporbance from those obta.i~md froln fertilisabion i',~te'r se. (iv) When both fami]ies are taken together, there is no difference between F, as compared with F a ratios either in normals or peculiars ik'Olll selfing, whereas there is a doubtful difference between/< and-Fa in norma]s frolu fertilisation inte.r se. When al]/Y~ ratios are compared with F a ratios there is a difference, viz. more F a sporophytes with the fldt chromosome number than F~ sporophy[es with the full chromosome number. I. Ax~n~sso5r-KoTT0 AND A. E. 61Am:DNE:~ 205

In F, I the chromosome number of only five peculiars has been obtained, i.e. an F a with 70 chrolnosomes gave all 1~'~ with 95-105. An/~a with 75-80 gave an F,~ with 95-110, and an fa with 80-85 gave three sporophytes with 96, 98 and 100-].02 respectively. TNts there were no full-nnmbered peculiars in F, I.

TI-IE INFEI~I~ED CIII~O~{OSOME NUBIBEg OF TI:[E ~ AND c~ SIDE Since, as shown above, a certes:in percentage of sporophytes occur with less than the hill chromosome mlmber, and s]nc~ from extensive data it is known that no gametophytes have less than 30 chromosomes, and also that the chromosome number for each plant is COl]Stant, all plants, moreover, being the result of fertilisation, we may assume that gametes, egg cells and spermatozoids, with less than 30 chromosomes, are produced. Whether a loss of chromosomes or some sort of irregularity or even reduction in the archegonia or antheridia occurs has not so far been cytologically observed. The antheridia (where, as will be shown below, the irregularities in question probably occur frequently) have very crowded divisions in the spermatozoid mother cells, and a.rc hence unfavourable for cytological examination. It is possible that cytological evidence may still be obtained from egg cells, since about one-halt~ of the egg cells ought to show some cytological irregularity. The assumption of the occurrence of gametes with less than 30 chromosomes is justified by the data given below, which show a sta.tis- tically significant difference between the ~ and c? side. This appears from reciprocM crosses with wdqa~'e type, i.e. a certain type plant of S. wdqa,~'e which is known to have the full chromosome number in all gametes (figlLred on Plate X, fig, 28 and Plate IX, fig. 24-). When the chromosome number of ~ and c~ gametes is inferred from the chromosome m~mber of the sporophyte resulting from the cross with v~@ct~'e type, the ratios of gametes with less than the full chromosome number to ~hose with the full number on the ~ and d side are seen in Table IV, When G~ and G3 of normals are used as ~ or c~ they were derived from C¢t selfed and (:~1-G2 selfed respectively. When G2 and C¢3 of peculiars are used they were derived from ~71 selfed and 6~1-~a st]fed, with the exception of nineteen sporophytes (sporophytes B-P in Pedigree V, and mentioned below in family B, pec. G,,), which were obtained from G~ fertilised i~,te,r st, (~, then used in the cross. The breeding results show that: (i) Sporoph?~es with less than the fldl complement are obtained when the gametophytes from c,J'i.sl)~ 206 Inheritance of Apos'pory i~ Scolopendrimn vulgate mu,ricatu,m (family A) and from 10/24 (family 113) are used either as -9 or c~ in the cross with wdya,'re type (stable type with 2n = 60, n = 30). (ii) The percentage of sporophytes with the i'nll chromosome nmnber is not ~he same for the reciprocal crosses with vulga're type. A higher percentage of fnlI-lmlnbered sporophytes is obtained from the 9 side than from the

TABLE IV Showing 'ratio of sporoph,ytes wiJ~ less th¢un full Io those wiJ~ ,fidl &romosome, ,nwmber, obtcd'J~ed as th,e ,i,m,mediate ,result of,reciprocal e,rosses qf each, ga,m,eto- l)hytie generation with ~mlgare type No. of sporophy~es No. of sporophytes with wi~h ehl'omosonle no. otu:omosome no. ,~ A___ Less Less ~htm full Full tha.n full Full Gametophytes of fiemily A as ~ and (~ -9 NormM G1 5 4 c7 Normal G1 a, 8 1 G 8 0 a~ -- -- c<., 6 0 Poe. G1 0 0 Poe. G1 G 0 2 G Gamelophytes of fa,mihj B as 9 a~ld (9 Normal O1 1 2 c~ Normal G1 5 0 Poe. 6l1 12 13 Poe. 6' 1 2 1

G 5 1 G No. of Percentage of No. of sporophyges sporophy|;es sporophy~es with witch with chromosome no. eln'omosome no. ehl'o/llosollle no, A .A Less Less Less than than ~han full Full full Full £ull Full Pamilles A ang B together Nortm~l G1 (i 6 50'0 50'0 c~ NormM G1 5 0 G~ 8 i 88.9 i.[-1 G~ 8 0

Pee. O1 21 13 01.8 38.2 Poe. G~ 2 l (i 20 6 76,9 23-1 (4 -- -- G 3 5 1 83.3 16.7 ("a -- -- c~ side of all normal gametophytes in G1, G~ and Ga. In the gametophytes giving peculiar there are not many data for the c~ side (only three plants). As ~he numbers go ~he 9- side here also-h'~s more gamete~'~ with ~he full number than the c?. If the G1 giving normal and peculiar are counted together the ratio of short-numbered be full-numbered gametes is On the 9 side ...... 58.7 : ,11.3 ~o, 0n the d' side ...... 87.5 : 12.5 %. I. ANDE]~SSoN-KOTT0 AN]) ' A. E. GAIlY.eNJOIn,t 207 Another featm'e shown in Table IV is that when the ratios of less- than

]DO ~2 I~ATIOS FI~Oi~'I SELIOINC~ AND FEI~'_PI£,ISATION ffNfl'EF~ ~S'E AGI~EE ~¥ITI[ EXPECJTATION ON ~_ AND fi~ SIDE I~AT]OS IN GI? \¥e may ]C[rst compare the ratio of short-n.ulnbered to fldl-numbered sporophytes obtained from selfing eleven G1 gametophytes with theratio of sporophytes obtained from using the same eleven C71 gametophytes as 9 in crosses with ,.~dgc~'e type as c~ (i.e. fldl-numbered on both -9- and c? side). The G 1 gametophytes as 9 x v'~dgc~'e type c? gave, as set out below, sixteen short-numbered and fiReen fldl-numbered sporophytes, a ratio of about 1 : ]. If the 9 side is thus about 1 : 1 and we take the c? side of the ¢~1 gametophytes to be 87-5:12-5 per cent. (for normals and peculiars), the expectation on selfing these eleven gametophytes would be a ratio of about 15 : 1. The nmnber obtained, 26 : 14, does not agree with this. If these nmnbers from selfing are scrutinised for normals and peculiars in the two families of these eleven gametol?hytes and are compared with bhe calculated numbers based oil the various data for the 9 and d side, it is apparent that the obtained nmnbers do not agree with any expectation; in the numbers obta.ined here (as in the case of these G~'s together) the 60's are more frequent *,ban hi the calculated ones. Furthermore, if we compare the ratios fl'om all G 1 game~ophytes selfed or fertilised i.nte~' se (see Table III), for all normals and peculiars 208 Inheritance of Apospory in Sco]opendrimn vulgate bogether or separately, we find again a higher number of 60's in ~he observed ratios than in the cMculated .ratios (with the exception of

TABLE V Rat,io of sho.rt-.n,u.vd)e.red to f~dl-n,u,mbered F~, Slmrqphytes obtained from the same 6% se}fed and ,used ~t,s ~ ,i,n cross ,with wdgare type (with, .full-n'tm~,bered gametes on both, 9 and ~ side) F~ fi'om F l 9 #. from selfing x .mdgare ~ypc

r Short; Full Shorf. Full g 1 in fa,m. A, normal 6' l no. 6 6 1 '2 "2 3O 2 0 2 ] g I in f'~m. B ..... A t9 '2 l 0 2 ([1 in t:am. A, pec. ,, 28 0 6 2 0 36 1 l 2 0 G~ in faro. B ..... ll 3 3 3 3 17 2 2 0 '2 30 4 o 1 31. 2 0 1 1 32 2 0 2 1 A16 2 0 1 2 TotJal 26 14 16 15 peculiars from fertilisatibn inter se, where less 60's are obtained than expected, the 9 side giving 62 : 38 and the ~ 67 : 33).

DO J~'3 I~ATIOS FROM SELFING ANI) FE~TILISATION ~INTE.t~ ~S'E AGI~EE WIT~ EXPECTATION ON ? AN~ ~ SIDE aATIOS I~ ~? For G~ gametophytes giving normMs the only data for the ~ and c~ side appear in family A. Since the female is 8 : 1 and the male 8 : 0, no normals with 60 chromosomes would be expected in F a. From G~ selfed in family A a ratio of 33 : 12 was obtained, and from fertilisation i,nte~' se 8:3 (in family ]3, 19:13 and 3:3). As inE 2wethus have here more full-numbered sporophytes than is expected on the ratios of gametes with the full chromosome number in G~.

ON THE POSSIBILITY OF SOME ~% GIVING MORE GAMETES WITH TI-IE FULL OItl~ON[OSOME NUM]3EI~ TI{AN OTI{EI~S The number of sporophytes obtained from eacu gametophyte upon selfing, the chromosome numbers of which were asoerbained, is not large, but, as seen in the pedigree charts, each G1 and G~ on the whole gives sporophytes with different chromosome 1lumbers. An exception is found in the peculiars of family A (Pedigree tI) where one G1 gave six sporophytes, all wibh 60 chromosomes. Since only five G, giving peculiar were selfed in ~his family, and since the number of sporol?hy~es obtained was smM1, it must be left open whether the difference in this G, gametophyte I. ANDE:R.SSOi',LKOTTO ~\u) A. E. G AmDNEg 209 or ill the peculiar G~ of this family is of statistical importance. For the 6/l ill family B giving peculiars and for the G, giving normals in families A and ]3 the difference is not statistically significant. The exceptional gametophyte referred to above, whi& ga,ve only sporophytes with the full e,hromosome number, does not constitute a type which ntay be compared with 'v'u,lgare type, i.e. having a permanent full chromosome number on both 9- and

_Do NORMAL SPOP~OP[IYTES ~VITI-I 60 OI-IE,OMOSOMES GIVE TKE SAME I~ATIO OF SHOP~T-NUM]3EI~,ED TO FULL-NUMTBEP~ED SPO~OPI:IYTES AS THE SHOI~T-NUM]3EI~ED SPOI~OPI~YTES ? The numbers for normals from 6<. selfed for the two families are set o ut below. They show a statistically significant difference in the number of sporophybes with the full chromosome number obtained from/#~ sporophytes with less than 60 chromosomes as colnpared with the number fl'om F. sporophytes with 60 chromosomes. The number of Fa sporoph~es with less than 60 chromosomes is larger from F~ sporophytes with 60 chromosomes than froln F~ sporophytes with less than 60 chromosomes. The same applies to the individual families (A and ]3) which do not differ from one another in results. Faro. A Faro. ]3 Faro. A + B /~a Fa Fa /~e sporophy~eswith less than 60 chromosomes gave 21 : ll 12 : 13 aa :24 F= sporophy~es wit,h 60 chromosomesgave 14 : 2, . 20 : 0 34: : 2

IN TKE PECULIA.IgS, 1)O TKE 60 OHROMOSOME _F2 SPOI~OPHYTES HAVE AN ~3 WITH THE DOUBLE CHI~O~,[OSOME NUMBEI% AS FI~EQU.ENTLY AS TKE LOWEI{ NUh{J3EI~ED if2 SPO:gOPKYTES? In Fa none of the /7'2 peculiars with 60 chromosomes doubled the chromosome nuul.ber in Fa, whereas some of the F2 with less than 60 doubled, The nmnber of sporophytes was: lea widl less /~a wi~h ~h~n double double elu'omosonle chromosome lln~llber nu~nloer 2'I,, nineteen sporophytes wil,h less than 25 24 60 chromosomes togel,her gave F 2, nine sporophyt,es with 60 chromosomes 16 0 gogebher gave 210 Inheritance of Apospory in Scolopendrimn vulg~re

DoEs IT MAKE ANY DIFF.EI~,ENCE TO THE :PI~OGEN~r (F3) IN Y~ESPECT O17 CHI~OMOSOME NUMBEI~, ~V~tETI-[Eg GAMETOPHYTES OF THESE 1i'AMILIES (A AND B) ARE USED AS ~ OR c~ 1N TgE OI~OSS wi'rH VULOJn~ TYPE? It has been shown above that both the ~ and d' side of the gametophytes fix these experimenl)s have a certain proportion of gametes with less than the expected chromosome number. This appeared from the chromosome number of the sporophy~es which were (~he immediate resN~ of crossing these gametophy~,es as ~ and c? with 'vulgar~ type. It, may be asked if the sporophytes thus obtained subsequently behave in

TABLE VI )lode of breeding Chromo- or i~s [lesull,ing some no. , ganlei,o- No. of cesuli.ing spor(Thyl,es , wil,h sift. no. ,)_¢ spf. l)hyl,es less l,hlHl (;0 : Ill) (:hI'oIlIOSOIIIeS (1) Normal and peculiar o xvulffare type Faro. A. Normal G 1 no. ~P~ ~'.~vulgccrc ~ylm 470/3 [ 60 Selling 3 : 0 ,, ,, 6 × ,, 605/31 55-60 'inter se ,1 : 0 inter se 6 : 0 Faro, B. ,, A 19 × ,, ld2/30 60 inter se 7 : 0 Poe. ,, -- × ,, 24/31 50 Selfing 5 : 0 (2 pee., 3 nm'mal) ,, ,, 11 ".: ,, 71/30 55-60 Selfing 8 : 1 (2 pee. 6 normal : 1 normal) ,, ,, 11 × ,, 139/32 60 i'nter se '[ : 0 (3 normal, 1 pee.) ,, ,, 31 x ,, ,175/31 G0 inter sc 2 : 0 (2 normal) .... 17 >," ,, 536/31 60 Selfing 6 : 0 (6 normal) inter se ,1 : 0 (4 pee,) 30 .'," 534/31 60 Selfing 2 : 0 (2 normal) (2) Vulgm'e t,ype ~ ×normal and peculiar c~ V.ldga.re ~ype ~ :< nomml, (¢~ in faro. B c~ 205/30 50 inter se 3 : 0 ,, :

~:- For selfing and crossing of ~hese see p. 208.

~he same w~y whether they are derived from ~t~ese game~ophyt, es (normals atld peculiars) used as ~ in the cross with vulga,.re type, or from these gametophytes as 3' fix the cross with wdga,.re type. The result, fl'om reciprocal crosses is set out in the la,sg colmnn of Table VI. The restflts of reeiproca.1 crosses are not significantly different. When normal and peculiar are used as 9 in the cross, a,ltogether fifty-one sporophytes have less than 60 chromosomes a,~d one has 60. When normal and peculiar are used as (? nineteen sporophytes have less than 60 chromosomes at~d three have 60. Both normals and peeulia,rs are similar. As far as the data go, there is no indication that progeny from 60's differs fl:om progeny of lower-numbered sporophytes. I. AND,~I~.SSoN-KOTT0 AND A. E. G-Am])~,TE]?, 211

ON THE OCCUI!{I~ENCE OF SPOI~ANGIA CONTAINING SPEP~MATOZO.[DS INSTEAD OJ~~ SPOI~ES The F:, t'1"o111 the cross between normal and peculiar, and the hetero- zygons F 2 l?]angs, show a very remarkable feature, consisting in the development of sporangia with a, content of sperlna~ozoids (Plate VII) instead of spores. These sporangia occar among the normal ones with a frequency of about 0.4-0.5 per cent., or sometimes higher. Both occur in the same sorus and are equally well developed as to stalk, wall, sequence of divisions, etc. The only difference is that spermatozoids develop instead of spores. There are usually sixty-fo,r sperlnatozoids, replacing the same number of spores; but ill one or two sporangia only thirty-two could be counted. In one instance, spermatozoids were almost certainly formed when the spore cells were still joined in tetrads. The spermatozoids borne in sporangia are slightly larger than those borne in antheridia. Sporangia with spermatozoids have been found in two sporophytes, the results of vulga, re type ~ x g 1 peculiar c?; in three heterozygotes between peculiar and normal derived from one of these sporophytes, but not in three homozygous normals which were sister plants from the sgille; further, spermatozoids were found in fourteen sporophytes, the results of crossing (I~ peculiar ~? and vulga, re type d. No sporangia with spermatozoids were found in five sporophytes, the results of crossing normal 6~:[ by vzd,ga, re type reciprocally, or in t~en sporophytes from normal G~ selfed. From G2 of peculiar x '~tf,~cjgre type, the four sporophy~es investigated had spermatozoids. It has not been possible so far to use the spermatozoids borne in sporangia for fertilisa.tion.

ON TIIE lgELATION :BET\'VEEN THE DIFFEI~ENT QUANTITIES OF q']~IE GENE lPOI~ PECULIAI~ AN]) ITS ALLELOMORP~ FOR NORh'IAL As regards the relation between different quautities of ttLe gene for peculiar with its allelomorph for normal, it, appears that what are pre- smnably fore' doses of the factor for peculiar are as recessive to one dose of normal as is one dose of peculiar go one dose of normal, inasnmch as normal sporophytes obtained fl'om &~, ~ and G3 carrying peculiar crossed wi~h normal, are normal. The Ga x normal is, however, of lower sl~a6ure and not so well developed as the sporophytes from G1 and G2 × normal; the former still show dolninance of normal, and there is no sign of the "peculiar" characteristics. As regards gene quantity and dolninance it is also of interest to find in these experimmlts that t~he hybrids fronl peculiar in one dose (d'l) and Journ. of Genetics XXXlI |4- 212 _['~he~'ita~ce of Apospory i'~ Scolopench'ium wtlgare in two doses (Go,) crossed with normal do not differ in the ratio of sporangia, containing spcrmatozoids to normal sporangia.

ON ]~ERTILITY~ SIZE OF PLANTS~ ORGANS AND CELLS 6'i of peculiar, GI and 6~'0 of normal crossed with v'tLlga,,rv type, give sporophytes with the full amount of spores which germinate well, as also do normal (/1, G2 and (d:~ selfed. Go of peculiar x 'v~dga,,re type gives sporophytcs of which the spores do not germinate, and ~.~ of peculiar x 'v'~@a,'re type does not as a rule develop spores, or if any are formed t,hey are badly develol?ed. Again the spores from the homozygous normal Sl?Oro- phytes (mentioned on p. 202) with 75-90 chromosomes do not germinate. The p'ceuliars develop no indusia, sporangia or spores in any generation. The sex organs are normally developed both on gamctophytes giving normal and on those giving peculiar in all generations, and both self- and cross-fertilisation takes place with equal case in all generations except in (;a of the peeulia,rs, where sporophytes f¥om sclfing or crossing with v,~dga.,re type are slow to appear, more noticeably so after self- fertilisation than after crossing with ,vzd.ga.~'e type. As regards the appearance of the normal sporophytes the presence of vzdgc~.,te type usually broadens the frond, and where murication is present it is less pronounced than in the homozygous mm'icatcd type. There is no increase in size or development of murication in the sporopbytes with two doses of murieated normal as compared with one dose, when both are in combination with the v~dqco'e type; that is, the same results are obtained from using .normal ga,metophytes with 30 a,nd with more than 30 chromosomes in crosses with w dga,.re, type. Sporo- phytes with four doses of normal with mm'ieation (from gametophytes with more than 30 chromosomes selfcd) and no wdga.~'e type, though good growers, are of reduced size and show exaggerated murication. In family A, sporophytes from pcmfliar ~:[1xvu, tga,'~'e type are similar to those peculiar (~'2x w@a,,re type. In family B the latter are larger than the former. Peculiar ~ x vzdya,,rc type makes a curious type with short, thick and narrow fronds, usually irregularly lobed and with uneven surface. The peculiar sporophytes have been described above (p. ]93). They are similar in size and development in all generations. When comparison is made of size of organs of limited growth, such as sporangia in the sporophytic generation and archegonia and antheridia in the gametophytie gsnera.tion, the measurements show that the ~. ANDKgSSON-KOTT0 AND A. E. GAiRDNEg 213 sporangia, are of about the same size whether fl:om sporophytes wit,h 45 or 60 chromosomes, and irrespective of origin. Archegonia and antheridia are the more easily compared, since they are well developed on all gametophytss, whereas t;he sporophytes with a high ehropmsome number generally give badly developed sporangia,. The fully-developed arehegonia and antheridia are of about the same size on all gametophytes with 30 chromosomes, whether the game~o- phytes give peculiars or normals. @ametophytes with a higher chromosome lmmber than 30 arising fron], llOrlual sporophytes have not been investigated, owing to the rarity of their occurrence. The archegonia of the gametophytes of the peculiar series (G1 ~xdth. 30 chromosomes to (2a or Ga with about 100 chromosomes) are all of the same size. The cells best comparable in respect of size are those of the stomat~a and the egg cells, and to a less degree those in a. certain part of the frond, for example the basal part of the leaf blade, or cells of a certain position in the gametophyge. Increase in chromosomes gives rise to no increase in size of the cells, whether in normal sporophytes of different composition or in normal sporophytes of different chromosome nmnber. The same is true as between the pecNiar sporophytes of the series F~-F,t, and also as between members of the gametophyte series ~'~. giving peculiars and G2, (~a and G,t from ]?eculiars and all gmnetophyges giving normal. The eompal~son only holds between cells of sporophytes of approximately equal age and development, or of well-established gametophytes. To compare the cell size of the pecNiar with that of the normal is difftcNt o~dng to the different type of cell. It is remarkable that the gametophytic cells of t,he leaf blade in the peculiar sporophytes are larger than those of their outgrowths when these are established as galnetophytes on soil. As the pemfliar frond grows out aposporously the cell size gradually decreases until the size typical for the Gx is reached. This is the only case where the size of the cell is affected. The different size of the fronds of normals, mentioned above, must, since there is no difference in cell size, be due go a difference in cell number. As mentioned on p. 212, the most sl,riking difference in size of the frond occurs in peculiar G:~ x v'u, lgcr,re type.

Discussion It has been shown in tile preceding sections that the gene for peculiar is allelomorphic go the gene for normal, a simple segregation occurring 14-2 214 I~alceritcc~ce of Apos~)o~'y i~ Soolopendrium vulgate in F o h'onl heterozygotes between the two. The gent for peculiar has a pleiotropie effect: peculiar plants are recognisable as such from the first leaf, and. differ from normals throughout their ontogeny; in particular they are eharacterised by the development of gametophyte tissue at, an ca,fly stage, compared with other ca,ses of apospory in fern,s, and the sporangium and spore sf,age are completely eliminated. Full sexuality is retained. In the heterozygotes between normal and peculiar, the normal development of the complete life cycle is dominant over the incomplete life cycle of the peculiar. The interesting fact that sl?ermato- zoids instead of spores are formed in some sporangia of the heterozygote shows that the gene :for peculiar in. combination with its allelomorph for normal ha.4 a second effect, i.e. for w.hat may be termed time of differentiation of sex. ]in this respect incomplete dominance obtains. It has been shown above that somatic apospory and failure of synapsis can be due to genetic factors. In other cases failure of synapsis is due to specific chromosome deficiencies. There is therefore no longer any ret~son to consider hybridity in itself as a cause of permanent apospory; unless through hybridity mutation, elimination or rearrangement of certain genes occurs. As in the case of other genes, modifying or comple- mentary factors may be present. Apospory may therefore appear either in diploid, or polyploid races. It has repeatedly been shown that polyploidy need not in itself lead to apospory or apomixis. In the peculiars, since 2~, sporophytes which are homozygous already show apospory and no increase in apospory occurs in. the higher polyploid series, it cannot be assumed that polyploidy itself is the cause of apospory. Moreover, gametes with less than the pre- sumable haploid chromosome nmnber carry the factor for apospory as well as those with the usual chromosome number. Polyploidy then is here the consequence of apospory and not ~Jice ve.rsa. Moreover, polyploidy does not lead to apomixis. The fact that apospory and asyn.apsis may be caused by Mendelian genes makes it easier to understand how the apomictic races which occur here and there in the botanical system may have arisen. A mutation from the normal to apospory or asynal?sis may occur anywhere. After such. a. mutation, if apospory is .recessive, and sexuality or partial sexuality still occurs, a recombination with other factors would occur on hybridisation with other normal races and a segregation in 2go of various new constant (aposporous) races would occur, besides norma]s. If a.pospory is dominant (as is possible, for example, in the experiments with Hie,r~tci~tv~ a,'t~'a..~ticl,e~tm,), and if there is retention of at lea.st partial ~[. AND~3gSSON-KOTT0 AND A. E. GAT]~,DN:E~ 215 scxuMity, various aposporous /¢'t races would originate in the ease of either pa,rent being hctserozygous for other characters. Further, it has been suggested by Darlingtson (1.932) thai) in totally a,pomictic races, new forms may arise through crossing-over or (as shown by Gustafsson, 1934) by the two chromatids of one chromosome after association, passing to the same pole in pseudo-homotypic divisions. The present paper shows that disturbances occur at gamete formation. It is possible that these disturbances are comparable wil)h the disturbances in development o1' function of the sex organs which are forum in connection with other cases of apospory. In cases of i,~duced apospory such secondary disturba, nces need not occur, as has been shown, for instance, by I-Ieilbronn (1927, 1932) and Manton (1932) for ferns. When they do occur, as shown in mosses by Wettstein (1924, 1928 a,), they are probably caltsed by polyploidy and[ an inharmonious kern-pla.sma relation, with reslflting monstrous growth o1' non-development of sexual organs. Diploidy or polyploidy of the galneto- phyte does not as a rule lead to apomixis*. On the otsher hand, where obligc~go~'9 apospory occurs in ferns, it5 is followed in all cases investsigMsed by apogamy (SOlnatsic apogamy or part:henogenesis) or some form of disturbance at; the sexuM stage, t:he latter also occurring in the pemtliar. It, is therefore possible tshag tshe appearance of apogalny in cases of obligatsol'y apospory otsher than the "pemfliar" ease is due to tshe effect5 of a factsor primarily ca,ltsing apospory. In tshe cases of obligatsory apospory in organisms, such as ferns, witsh the two generations well developed, a secondary distltrbance may oecttr sooner or 1Mser at5 the sexual stage. If ig occurs early at5 tshe sexuM stsage, the result, will be t:he loss of t:he entire sexual organs; if late, a loss of proper gamete formation, non-functsioning of tshe gametes, or irl'eglflal'itsy at their formation (as in t:he peculiar) t:hough not: leading t:o non- %nctioning, would result:. The same physiologica,1 process which leads to t:he loss of the whole sexua,1 organs, or t:he fMhtre to form good gametses, may also lead to the development5 of an apogammts outgrowtsh, viz. a nerve sporophyte. Another physiologiea.1 process leads to the non- flmctioning of the gametses (in regard t5o sexltalitsy), and the asexual development of the gametses (egg cells) into sporophyf,es may occur, gha~ is t,o say, parthenogenesis. Where the disturbance on the other hand occurs as late as gamete formation, and is not lethal, sex function may 1 Among excepl,ions go this l'ule may be menl;ioned the t~egraploid gamel~ophyl~cs of Polypodl.w,i. a'lt'rcwm, (Heilbronn, 1932) and l~he bivalent~ races of Phase.am, c,m'~pid~ttu..m (Springer, t935). 216 I~,he~'ita%ce of Al)osl)o~'y i~z Seolopendrium vulgate not be upset and 11o apogalny or pa,rthenogenesis occur; in other words diploid gametes are formed which may be ferl.ilised, as for example in angiosperms in Zea Ma, ys (Beadle, 1930) or as in the case of the peculiars where a ccrtaill percentage of presumably unreduoed gametes are formed. In the a,llgiosperms it :is the rule ~ that apogamy or parthenogelmsis follows on somatic apospory, and various sexual disturbances, such as d.cgeneration, occur in plants whore the heterol~ypic division is more or less unsuccessfnl. The following examples may be mentioned. In Dat,~vr~, (Blakeslee, :1928) the plants which are homozygous :['or the factor which prevents pairing are sterile ill both eggs and pollen. ][11 certain dwarf wheats and oa.~s (Huskius and Hoarne, 1933) where asynapsis is produced l;ltrough loss of a specific pair of chromosolncs, irregular sized sterile pollen is produced ,~nd the breakdown of the nucleus may occur at any st;age aft,or diakinesis. In Zea Ma, ys (Beadle, 1930) few megaspores and microspores ~re functiomd, a,nd an analysis of the progeny showed that the megaspores were often diploid. In seine pollen grains of F~latostema. a,c'wm,i~.at,wm, and l~Vickst~'oemia, i'~dice (Strasburger, 1910) whore spores are forlned we find that the nucleus of the pollen grain divides, but degeneration sets in. On the female side, for example in Ocher.a, ~,~dtiJl,o~'a (Francini, 1928), the diploid egg cells of the unreduced embryo-sacs degenerate. In other cases apogamy follows, 'i.e. various cells of the 9 gametophyte, the egg cell, the synorgids, the antipodals, etc., grow ottt apomictioally. ]~actors as those described above, which primarily cause apospory or apomeiosis, should naturally not be confused with factors for sterility, where d.egoneration of the mega- or microspores occurs after a normal meiosis, or incompatibility exists. If apomixis and disturbances other than apomixis at the sexual stage (including the process in the peculiars) are phenomena of the same kind, only dithering in degree, the data here presented for the pecNiars and the crosses with v,~dqa~'e, type would show the relation between apospory and the succeeding processes (apomixis and sexuM disturbances). Bergman (1935 a), investiga.ting Hie.ra,civ.,m, ~mbcll<~t,wm, came to the COll- clusion that the primary phenomenon is the occurrence or non-occurrence of the reduetiou division, b~tb siizce i~o genetical data were a.¥a,ilgble this could not be proved, and he assumed that the gone or genes ibr asyndesis and apomixis in H. ~bellc~,t'~v~, are "nahe lniteinander verbunden" or even identica.1. The first conclusion is, I think, substantiated by the

Among late few except, ions t,o ~his rule m~y be mentiolmd ~l~eo~lodo~. hislJid.l~s (]3ergma.n, 1935 b), where the embryo-sac req aires tbrl,ilisatio~ tbr il,s developmenb. I. ANDEt:tSSON-KOTT0 AND A. E. C4AII~DNE;~ 217 present investigation. In the peculiar< the results of the breeding work and cytological data show, however, that the gene for apospory (which is comparable with a, gene for asynapsis) is not identical with a gene for apomixis (or for sexual disturbance) in the'sense that the s~mm gene always causes both phenomena, and its allelomorphic gene neither. Nor is thcce a, separate (linked or independent) gene for a,pomixis, as the da,ta show. The disturbances at the sexual stage are nevertheless probably introduced by the gene for apospory, and it may be assumed that the lowering of the chromosome number at the sexual sta.ge is the result of disturbances in the plasma or in the intricate relations between nucleus and pla,sma, It would[ thus seem possible that the gene a for peculiar development would prima.rily caase apospory, and secondarily, through the plasma, upset the events of the nuc]ea,r phase at, sex formation; this upset would be severe enough to persist in the peculiars, and also to be transferred to the nonnals on crossing, and to occur rhythntica,lly just at the sexual stage. The relation between apospory and the succeeding apogamy or sexual disturbances would then be physiological-developnmntal. Since in the experiments related in the present paper the disturbances at gamete formation do nob take the form of apomixis or irregularities lea,cling to non-functioning in the sexual sphere, and more especially since the disturbances are not so gross as to lead to gametes with a content of practically any chromosome number, such as might be expected from fusion of nuclei or very irregular division, we hold it to be unlikely that the disturbances at gamete formation are here comparable with apomixis or various phenomena leading to sterility as related above. This contention is borne out by the deduced action of the peculiar gene. It may also be taken into account that the peculiars show a much earlier development of gametophytes (or gamstophytic tissue) than do other aposporous ferns, and especially that the whole development of the peculiars is altered., whereas other aposporous ferns do not differ from the corresponding normal form in other characters which can be attri- buted to the same cause as the apospory. gametophytes with 30 chromosomes give rise to gametes with a chromosome number varying from 15 to 30, but never outside these limits. It seems probable therefore that the divisions may be partly meiotic and partly mitotic in character. Some divisions may be wholly mitotic, others wholly meiotic, giving the extreme chromosome nmnbers, while a,n intermediate conditiou would[ give rise to intermedia,te numbers. 7For example, if 20 chromosomes paired and 10 divided without pairing, 218 Inhe'rita'r~ce of Apo~'po'ry i~'b 8colopendrium vulg~re the resulting gametes would have 20 clu'omosonles. In the succeeding divisions all chromosomes may be presumed to divide mitotically. it is well known that hybridsmay either show pairing between all chromosomes, or complete non-pairing; and between these two extremes there is a series from those with most chromosomes pairing to tl~ose with scarcely any pairing. Furthermore, the unpaired chromosomes may divide equationally at both first and second meiotic divisions. Among examples may be meni;ioned Pyyae,ra, (Federley, 1931), Viola (Clausen, 1926-7) and Rosa (T~ickhohn, 1922). ]it is of special interest in connection with the chromosome number of gametes in our experiments that the pa.iring between chromosomes may vary in different cells, as shown, :for example, in Pygae,ra, (Federley, 1913), Hie'racium bo'reale (gosenberg, 1.917)and many other cases. That the nmnber of gametes with the Nil chromosome mtnlber is different on the 9 and c? side in our experiments is probably due to differences in freqnelmy of pairing, or some such process, on the two sides. This is in analogy with cases in angiosperms, where several instances have Been found in which p~iring is complete in the 9 organs, but defective in the 3 orga.ns, e. 9. Viola, o'rpha,~id,~;s (Clausen, 1930) and Pygae,ra, (Federley, 1931). The reverse obtains in other cases, e. 9. in Ta,raxacu,m, No,rdstedgi and Kalbfussii (Gustafsson, 1935). Since no lowering of chromosome nmnber occurs during on~ggeny of sporophyte or gametophyte or in the peculiar at the transition between the two, and since crosses show that the immediate product of fertilisation is a proportion of sporophytes with less than the double gamegophytic chromosome number--reciprocal crosses, moreover, giving a different nmnber of such sporophytes--it follows that the point of gamete formation is here the place of an attempted reduction in chromosome nmnber. That some attempt at a reductionM process might be made at the sexual stage in the peculiars is indicated by the action of the allelomorphic genes for normal and peculiar. The gene for normal (dlelomorphic to peculiar) evidently has two main actions: (i) it causes long complete life cycle, and in this respect is completely dominant to the contracted, incgmplete life cycle of the peculiar; (ii) the time of sex differentiation is different for the two allelomorphs. The gene for normal causes the processes leading up to sex differentiation, figuratively speaking, a,[ a prolonged rate, sexuality occurring at the '~z stage, while f,he gel~e for peculiar gives a speeded up process, sexuality (in the absence of the sporangium and spore stage) occurring at the 2u stage. This is apparent in the (normal) heterozygotes, which show partial 3. A~DI~I~SSO~-KOTTO ha~)A. E. GA~[r~D~J~:~ 219 dominance in this respect, i.e. sexuality occurs at two points in the heterozygotes, since spermatozoids are found ill sporangia, and spermatozoids and egg cells on the gametophytes. Since galnetophy~e formation is not necessary for differe~ltiatiou of sex, the development leading up to sex differentiation must be considered for f,he life cycle as a whole. The point of sex differentiatiOl~ i~l the peculiar thus corresponds to t,he spore stage in the normal, and hence a reduction ma, y be initiated at the sexual stage of the peculiar. Another ease where meiosis may be said to occur out of place may be mentioned here, viz. in hybrids of Drosophila, pseudo-obscu,ra (Dobzhansky, 1934:), and it is of interest that the frequency of bivalent formation is affected. The frequency of bivalent formation is higher in hybrids between some races than in those between others. There is also a difference between reciprocal hybrids, probably due to a maternal effect. In pure races meiosis takes place in nests of 32 cells, in (race) A 9 x B c? hybrids in nests of 32 or 16 cells, and in B 9 x A c~ hybrids in 16, 8 or even ~t cells. Thus meiosis may take place at a stage five, four, three or two cell generations removed from the primary sperlnatogonia. The precocious occurrence of the growth stage and meiosis, according to this author, indicates a disturbance of the time relationship between the various processes whose normal sequence is necessary for the normal course of spermatogenesis. It may be asked why, in the experiments with the peculiar, the normals, both homozygous and heterozygous, derived from the cross with the peculiar also show this feature at the sexual stage. There is no segregation in this respect anywhere, as Pedigrees I and III and the data on p. 200 show, and the feature is introduced both by the 9 and c? side. It may be assumed that the gene for peculi.ar, as opposed to its allelomorph for normal, primarily has the two effects mentioned above. Secondarily it causes an alteration in the processes leading to reduction in the chromosomes. In other words, it seems that the whole physiological-chemical-developmental processes in the plant are altered to such a degree by the peculiar gene that the plasma, or intricate relations in %notion between nucleus and plasma, are severely upset, for some time, or even permanently (see below). Hence a more or less ttnsuccessN] reduction at the sexual stage in the peculiar and a gra,nsmission and per- sistence for some time of an attempted reduction at the sexual stage in the normals after crossing. The sexual stage has become intimately connected with the reduction stage. The attempt at a reduction at the sexual stage--or perhaps more 220 .[~,herita~ce of Apoal)o'ry i~ Sco]opendrium vulgate correctly, the failure be retai~ a eon~plete reduction at this point, and the non-segregation of this phenomenon., can be compared with the Dauermodification phenonienou investigated by Jollos for Prol,,ist~b (1.913-34 b) and D,roso,~fltilcb,mda, noyaster (1931, 1932, 1.934 a) and by other authors for other organisms. These Dauermodifications are induced by temperature, X-radiation, poisons, etc., and it is characteristic, probably for all of them, that they sooner or later disappear. In Protist(t, repro- ducing veget'~tively, they persisted during thousands of divisions, but after fertilisatiou th%~ disapl?eared sooner or later. In Drosophila,, of the four Dauermodifications induced by raised temperature, viz. dwarf growth, an alteration of the wings called "aerophme", crippled wings and an abnormal abdomen, the first (dwarf growth) lasted partially to/~'~, while the three others only lasted to F~-F4. The transmission only occurs through the ~_ side. It is of interest to note that these four Dauer- modifications phenotyl?ically correspond to known gene mutations. Abnormal abdomen was even obtained by a raising of the temperature, both as mutation and modification. The mode of inheritance of these Dauermodifications, according to Jollos, shows that they are caused by a slowly reversible "Umstimmung" in. the plasma and not by a gene (or genome) alteration. On the other hand, in crosses between species and genera, such as, for example, in Ch'siu~ (Correns, ]909, 1928), mosses (Wettstein, 1928 ct and b) and Epilo- biu~, (~lichaelis, 1929, 1932, and works by Lehmann, Schwemmle and others) where l?h~smatic differences have been shown to occur, there is nothing to show that these plasmatic differences may not originally have arisen by alteration in the gene or genome (Jollos, 1931). This is indicated by the Gets from El)i~obi~m, where the plasma of one species may become in some degree altered by the genes of ~mother species. Moreover in Li,mnaea, (Boycott, Diver and co-workers, i930) it has been clearly demonstrated that mendelian genes change a non- corresponding plasma during the course of a single generation. It, seems possible that plasmatic inheritance and Dauermodifications are in principle of the same ~tature (lVIichaelis, 1932, ]933; Jollos, 1932). Since in these experiments reciprocal crosses with peculiar behave in the same way, and it is probable that no plasma passes over to the hybrid fl'om the c~ parent, it must be concluded that the behaviour at the sexual stage is primarily due to the peculiar genome. The relation between this genome on the one side and the normal plasma and normal genome on the other is conceived to be such as to alter the usual sequence of events not only in the hybrid but also in all the offspring, possibly in the manner ~[. ANID~.I~SSoN-Koa?TG AND ~A. _E. GM:t~DN.I~I~ 221 of a Dauermodificatciofl. Moreover, since l,he progeny fl'om tche hybrid (205/30) between v,~dgc~,re tcype ~ and normal Gt contemns sporophytces witch less tchan the normM chromosolne number (set Table IV) itc may be inferred thatc tche uucleus of bhe normal progeny from t;he cross betcween normal a~ld[ peculiar has been affected, and transmil, s the tmusual fea.l,ure ate tche sexllM stcage. The peculiar gent Mters (more especiMly, shortcens) tche developmentcM processes of tche whole life cycle dO tchatc tche sexuM stcagc replaces tche sporangial stage. The poinl~ of reductcion is thus retcained in tche peculiar, and now coincides witch the sexuM stage. The tcenacity with which tche ]?langs in the present~ experiments keep to their presmned atctcemptc a,C a reductcioa is strengtchened by the cytcologicM datca given by Gustca.Nson (1935) ~(qlich show tcha.tc tche steep from meiosis t;o mitosis is 11015so easy too tcake as tchat, on Darlingtcon's view (1932), from mitcosis too meiosis. Some factcs for tche families (A and 13) witch peculiar may now be briefly mentioned. Itc is probable tchat a,ll gametcophytes give galnetces witch a chromosome munber varying within a definitce limitc. If tche tcwo families are tcM¢en tcogetcher, tche different ratcios in. all instcances show a higher percentage of sporophytes witch less tchan tche full cllromosolne nmnber than ~dt)h tche frill chromosome number. The same s,pplies too M1 but one of the ratios for the separate families, and tchis ratcio is on tche borderline of significance. The ratios in tchese tcwo families, A and 13, do note fitc witch tche expectca- tion based on the ratcio for tche ~ and d side, as obtcained froln crossed witch v.u,lga,,re tcype (a tcrue-breeding type witch all gametces having 30 chronmsomes). The ratcios in families A and 13 show a higher percentcage of sporophytces with tche full chromosome number tchan would be expectced. Furtcher, l)he number of sporophytces with tche full chromosome lmlnber increases in /V~ as compared with F~ in families A and B (if the numbers for both families are taken togetcher); bntc tche number remains tche same or possibly decreases on tche ~ side (as shown by crosses witch ,v~@,,re tcype). On the d side, as far as the munbers go, tche number appears to remM.n the same. Though tche numbers for t~he ~ and d side are tcoo small too all.ow of a definitce conclusion, it may be assumed on the available da.t~a Chat the differences in the ratios a.re due tit)her to selective fertcilisatcion for chrolnosome munber between ga,metces in families A and 13 and[ in tche crosses wit)h vz@a're tcype, or tchag families A a,nd B show tche resnltc of tche actcual nmnbers of tche gametces formed with differentc chromosome numbers, while the result obtained from tche cross witch v~dga,,re tcype is impaired by selective fertcilisatcion, or vice 'va'rsc~. 222 [~]~e'ritcc~ce of A1)osl)o~'y i~ Soolopendrimn vulgate For the increase of sporophytes with the full chromosome number in Fa as compared with F2 in families A and B selective fertilisation may be similarly assmaed, or there may be a difference in actual ratio of gametes formed with different ehronmsome nmnbers, as a consequence of different degrees of pairing. However, all antheridia look normal, the spermatozoids of the difl':erent generations all look the same and seem equally active. Fm'ther, all archegonia and egg cells are well developed and no abnormalities have been observed either before or after fertilisa- rich, the latter occurring with the usual ease. These facts, though not excluding the possibility of selective fertilisation, diminish to some extent the probability of this process occurring. It may also be remembered that, thougla an increase occurs in F 3 as compared with F o when both descendants from fertilisation i~zte,r se and from selfing are taken together, the numbers from selfing on the one hand show no such increase, and[ those from fertilisation i'~te~' se on the other show a statistically doubtful increase. It is therefore possible that tire actual ratio of different gametes formed varies in successive generations. These facts, however, make it unlikely that any gametes are eliminated owing to their possessing less than 15 chromosomes, through elimination of chromosomes. However, whether the decrease of gametes with less than the Nll chromosome number in successive generations in families A and ]3 is explained by selective fertilisation or by less frequent pah'ing of chromosomes, the female and male sides, as shown by crosses with v'~dgc~'e type, remain unaltered in successive generations. This points to a permanence of the processes responsible for it in the generations so far obtained. Though the numbers are small, it is interesting to note that if the _~ and d gametes are counted together we have the same ratio of gametes in G1 with less than the full chromosome number in both peculiars and normals (see p. 207). Further, both peeuliars and normals have a higher percentage of gametes with less than the Nil chromosome number on the d side than on the 2 side. From the results it may be concluded that: (i) Both ~ and d side of normals and peculiars transmit the tendency to an attempt at a reduction division at the sexual stage. (ii) The transmission of such a tendency is the same on the 2 as on the d side (p. 210). (iii) The effect of the transmission is the same for normals and peculiars if ~ and d~ G1 gametes are taken together. (iv) The sfl!ect, i.e. gametes with less than the Nll chromosome number, is shown more on the d side than on the ~ side in both normals and peculiars. (v) The effect on the ~ side I. AhT:oEgssoN-KOT'J:6 AND A..E. GAIR,DNER, 223 in G2 compared with 6'i in norm~ls and ~o and G~ compared with G1 in peeuliars is the same, or possibly increased in G2 and G3. The fa,et (p. 209) that normal sporophytes with 60 chromosomes give less sporophytes with 60 chromosomes tha.n do sporophyl;es with less than 60 chromosomes is a~ present unexplained. :Both give good spores and gametophytes wit,h 30 chromosomes, and it has not, been possible to determine the pa,iring of chromosomes in the sporangia, with any certainty, go see whether it in different for sporophytes with 60 and those with the lower chromosome number. The peeuliars show a, some- what similar behavionr inasmuch as no full-nmnbered peculiar wa,s obtained in F~ from an Fa with 60 chromosomes (i.e. 120 chromosomes in F:~ :5'ore F2 with 60). The F~ peculiars with less than 60 chromosomes gave F a peculiars, about half th.e number of which had the double chromosome number and hMf had less tha, n the double. The facts seem to indicate that sporophytes with less titan the full chromosome number give more gametes with the full number than do the sporophytes which themselves have the N]I number. For the peculiars the higher nnmber (highest= 120) may not be obta.ined, owing to mecha, nical difl3cubies in development of the sporophyCes with the highest chromosome number, since no simultaneous increase in cell size occurs together with increase in chromosome number and nuclear size. The behaviour in regard to cell size, with some othe~• results, are discussed elsewhere and some further inferences drawn i¥om the pr.esent data (Anderson-KerfS, 1936). In view of the -fact that gametes are formed with less tha, n the full chromosome nmnber, which Net, as developed above, points to a reduction or at least to a decrease in chromosome nmnber at the sexual stage, we have here to consider a type of alternation of generations which is new for ferns and corresponds to, that of diplontie Algae and a,ngio- sperms, i.e. the haplophase is here reduced to the minimum, a,nd consists of only one cell, the ga,mete. In other words, a fern from having been a diplo-haplonb has become a diplont.

~UMMAI~Y 1. A type of' Scolol)e,,nd,ri,um, v.ulgare , called "peculiar", is described. The peculiar type is recessive to ~he normal type, a, segregation of 3 normal to I peculiar being obta.ined in F 2 after crossing normal with peculiar. ]?~eciprocal crosses give similar results. 2. The gene for peculiar affects the whole development of the spore- 224: I~he~'ita~zce of Apo82)o~'y i~ Scolopendrium vulgare phyte. It determines the absence of sores, sporangium and spore sga.ge and causes obliga.gory somabic aposp0ry. 3. Obligatory apospory i~ ~he pectdiar is not re]lowed by apomixis. The consequeucc is that a series of generations of the l?ectfliars arises with an increase of chromosome number in each successive sporophytic generation. ~J=. Though l~he chromosome nmnber in snccessive sporophyte generations of the peetdia.rs increases, it, is not always doubled in each successive sporophyte generation. No elimination of chromosomes occurs during the development of the pla.n~s. Since reciprocal crosses between peotdiars and normals in these experiments on the one side, and with wd,ga,~'e type on the ot]~er, show the same behaviom' in ghis respect ig is inferred that bobh female (egg cells) and male side (spermatozoids) may have less than the gamegophytic chromosome number. The percentage of gametes with less than the expected chromosome number is larger on the d than on 5he 9 side. 5. Probably all the gametophy'~es (Ol) from t'he uormal hybrid (P1) between peculiar and normal show this irregularity at the sexual stage, whether the gamegophytes in question give normals or pectdiars. The same applies go the Go gametophytes both from normal and from pecn]iar F, sporophytes. There is thus no segregation for this phenomenon. 6. If the bwo main families (i:k and 13) are taken together all ratios in normals and peculiars, obtained from selfing or fergilisation i'~te~" se, in all generations, show fewer sporophytes with the full chromosome number than with less than the ftdl chromosome number. 7. The rat, ios in//':~ have a higher percentage of fttll-nulnbered sporophytes than the fie, if the numbers from selfing and fertilisat~ion i'*~te~"se are taken ~:,ogether. Taken separately, the mtmbers from selfing show no increase, and from fert'ilisation i,,zte~' se the figure is hardly significant, bug the nttmbcrs are small. 8. From crosses with v.u,lga,~'e type it, is inferred t,hat, the percentage of ~ and d gametes wil~h the fttll chromosome number remains analgered in t'he series C4~-G.,-Ga, or t'hat a small increase of the gametes with less than t'he %11 chromosome number possibly occurs in (22 and Ga. 9. it makes no differe~me go the progeny (//'a) in respeel~ of chromosome number whether gamet'ophyt'es are used as -9- or 6' in the cross xyith vuTga,re type. 10. A feat'm'e new for ferns has been observed, viz. the development of spermatozoids instead of spores in sporangia.. Sporangia with spores I. ANDE~,SSON-KOTT0 AND A. E. GAIR, DNE]~, 225 cud sporangia with spermatozoids occur togeghcr on the normal heterozygotes between peculiar and normah ] ]. This feature of the heterozygotes indicates that the pecaliars and lmrmals also differ in time of differentiation of sex, the heterozygotes showing incomplete dominance in t,his respect, viz. sexual differentia.lion in two places, in sporangia and in gamel, ophytes. 12. ]it is concluded bh~b the sexual stage in the peculiars corresponds to the sporangial stage in the normals, and that therefore a reduction divisio~ is atl;empted at the sexual stage in the peculiar. ] 3. It is assulned that the developmental processes in the pecnliars have become altered, so t~h~ those which lead to a, reduction are intimately connected with sex di:ffereatiation. i[~. The effeet of the peculiar gene on the plasma, or the intricate relations between this genome and the plasma, are, it seems, of s, ch a character that the developmental processes are not only altered in the peculiar plants, but the effect is also transmitted to all normal descendants after crossing with peculiar. Hence a more or less unsuccessful reduction at the sexual stage in the peculiar and a persistance, at least for some time, of an attempted reduction at the sexual stage in the normals after crossiug. 15. Since the chromosome numher is evidently lowered at the formation of a proportion of ~ and d~ gametes a type of life cycle uew for ferns ha.s arisen, viz. a diplontic instead of a diplo-haplonl, ic.

We wish 1:o express our thanks to Mr L. La Cour for his care in preparing the many cytological slides, and to Mr H. C. Osterstock for taking the photographs. To Dr F. G. Brieger we are indebted for helpful interest and to Dr F. W. Sa,nsome for calculations of prol)abilities.

REFERENCES

A~D~RSSO,~, I. (1923). "The genetics of w~rieg~tion hi a fern." J. Genet. 13, l. ANDERSSON-KOTT6, I. (1929). "A geneticL~i investigation in Scolopend.rhc~ vulgate." He.redilcls, i2, 109. ----- (1930). "V~riegatlon in three species of ferns." Z. i'~d,td~'t. Abslamm.- u. Ve)'e,rbLehre, 56, 115. -- (1931). "The gono~ies of ferns," Bibliogr, ge:~,d. 8, 269. --(1932). "0bserv~tions on the hflleri~nce of ~]?ospory and ~Itern~ion of generations." Svenslc bet. TidJcr. 26, 99. -- (1936). "On the comparative development of ~ltern~ting generations." Ibid. 30, h[.I. 226 Inheritance of Apospory in Sco]opendrimn vulgate BEAOLE, G. W. (1930). "Genetieal ,q,lld cytological studies of Meudclian asynapsis in Zea Ma, ys," @tologia, 4, 269.

-- (1933). "Further studies in as)~lal?tic ma.ize." Ibid. 4, 269. ]3:~ADr,E, G. W. aND N[eCLI~Too~c, ]3. (1928). "A genetic disturbs.nee of meiosis in Zeal, Mays." Ntis)me, 68, 433. BE]IGMAN, ]3. (1935 a). "Zytologische Stud]on fiber asexuelles I-Iie~'acium umbel- latnm.'" Heredilas, 20, ,t.7. ---- (1935 b). "Zytologisehe Studien fiber die Fortpflanzung be] den (:l,%ttungcn Leontodou und Picris." Nvensk bet. ~'idslo'. 29, 155. ]3LAKESr~EE, A. IO. (1928). Yea,rb. 6'ar~efl. Instn, 27, 42.

-- (1930). Ibid. 29, 39. ]3expecT'r, A. E., ])IVEI~, C., G~ns'i'aNo, S. L. a~D To~NXr~, F. M. (1930). "The inhorita.uee of Sillistrality in Limnu.ea pereflra." Philos. (l'ra~s. 2i9, 51. CLAUSEN, J. (1926-7). "Goner]eel and cytological htvestigations on Viola, tricolor L. a.nd V. a,rve,nsis Murr." Hereditas, 8, 1.

-- (1930). "B'Iale sterility in Viola orphanidis." Ibid. i4, 53. COR~ENS, C. (1909). "Zur Kemtgnis der I~olle yon Kern und Plasma be] der Verer- bung." Z. indulct. Absla, mv~.- u. Ve.rerbLehre, 2, 33]. (]928). "~)ber nichtmendehlde Vererbung." Verh. F. Int. Kent. Vererb. (]3erlin), t, ] 3I. D,,t~r~INGTON, C. D. (:1932). Recent Advance~ in (~tology. London. DO~ZIIANSKY, TII. (19340. "Studies on hybrid sterility. I. Sporluatogonesis in pure and hybrid Drosol)hila, l)seudo-obscwra.." Z. ZellJbrsch. 2I, 169. EKSTmt~D, H. (1932). "Ein Fall yon erblicher As3~ldese be] Hordeum." Nvensk. bet. Y'idslcr. 26, 292. EaNST, A. (] 918). Bastardieru, ng als U,rsache der Apoga, mie im P flanzenreich. Jena. FA~sIE~, J. ]3. and Dm~¥, L. (1907). "Studios in apospory and apogamy in ferns." Ann. Bet. 2t, 161. li'I~DI!mISEY, H. (1913). "Das Verhalten der CIu'omosomen be] der Spermatogenese der Sehmetterlinge Pygaera a,nachoreta, c,ttrtula und pifp'ct so~.wie eiltigen ihrer Basta.rde." Z. i~dukt. Absta.mm.- u. Vers?'bLeh,rs, 9, 1. -- (193]). "Chromosomeil'malyse der reziproken Bastards zwischen PycJa.era pigra, nnd P. c,u.rtula, sowie ihrer I~iieldn'enzungsbastarde." Z. Zellforsch,. 12, 772. ]i'mt~c~N~, E. (1928). "Fenolneni di aposporia somatica, di aposl?oria goniale e di embrionia avventizia in Ochna mult$flora." R.6'. Acted. Lines], 7, 92. GOWES, J. W. (1928). "Mutation, chromosome non-disjunction and the gene." Science,s, 68, 21]. G~c~o~'z, I~. P. (I90:i). "The redueiiion division in ferns." Prec. roy. Soc. ]3, 73, 86.

-- (] 904). "Spore formation in leptosporangi,~te ferns." Ann. Bet. !8, 4~5. ¢4USTAFSSON, ~. (1932). "Zytologisehe und experimentelle Stud.ien in der C4attung ff'a/raxac,u,m." tic~'edilas, i6, 41.

-- (1934). "Die Formenbildung der Tot~lapomikten." Ibid. i9, 259.

-- (1935). "Primary and secondary association in (l'a~'axac.u,m. '' Ibid. 20, 1. HE~Lmm~, A. (1927). "Uber expm'imentell erzeugSe Tetraploidie be] Farncn." Verb. V. Int. Bet. Kent. 2, 830.

-- (1932). "Polyploidie und Generationswechsel." Be,r. dtsch,, bet. Ges. 50, 289. I-loL~c-~m,~, I. (1919). "Zytologische Stud]on fiber die Fortpflanzm~g bei den Gat- tUllgen E?'i.(/erott und Eupatorium,." K. sve,nska VelenskAkctd. [hendl. 59 (7). I. AN_DEP~SSON-t(O-I~I.( AND A. E. GamD~:t~ 227 I:[~st~I~s, CJ. ii5. s,nd ;[-[~_l~NJ~, :E. M. (1933). "15{eiosis in ~sSmaptic dwarf o~l)s and wheaL" J. 1~'.. mitt. Soc, 53, 109. ,IOLLos, V. (1913). "Experimenl;clle Un~ersuclmngen an Ilffusoricn," .Biol. Zbl. 33, 222. - (192].). "Exporimelii~ello Progis{icnslmdieu." A,rch,. Protistc~d~:. 43, [. ---(1924). "Uni~orsllchuugen iibor Vavi~bilil~/t.l~ mid Verorbnng bei Arcollcn." lbid. 49, 307. -- (1931.). "Gonel~ik m~d Evolulfionsproblcm." Verb.. dlsch, ecol. Ges. ]931 p. 252. -- (.[932). "Wcitcro Ungersuclmngeu fiber die ex])e,cimon~clle AtlslSsung orblieher Ver~ndenmgen boi D)'osojd~ ila v ela~ o qos/er. Z. ind'u l,:l,. A bslc~,.m.m,.- 'u,. Vererb Lehre, 62, 15. -- (193~a,). "Inheriged cha,ngcs produced by heal~4reai~mcnl~ in Droso2)h, ila, mehmo- gaster." Geneticct., 16, 476. --- (1934:b). "])~uermodKikM, ionen und h{ul;slbionen bei Protozoen." Arch. Pro- tistenlc. 83, 197. I~'L~Ntro~, I. (1932). "Conla'ibul)ions l)o l;he cyl~ology of spospory in ferns. I. A case of induced apospory in Osmunda reqalis." J. Genet. 25, ,t.23. 1KIomk~r~ts, P. (1929). "Ubcr den Einflllss yon J(ern und Plasma a,uf die Vercrbung." Biol..Zbl. 49, 302. -- (1932). "Uber die Beziehm-~gen zwischca _Kern und Pla,sm~ bei den reziprok verschiedencn Epitobium-ig~sl)arden." Z. ind,u, kt. Abstamm.- v,. VererbLeh,re, 62, 95. -- (1933). "En~bwickhmgsgcschichl~lich-gcnel)ische Unl)ersuclmngen an Epilobimn. If." 65, 1 and 353. OSTm'~:~':Br~D, CJ. J:L (19]0). "]?url~hcr sl~udies on l~hc ~pogamy ~nd hybridisal~io~t of l)he Hieracia.." Z. i,~tdukl. Abstctmm.- q~. VererbLeh.re, 3, 2OA. ]~,n~nt¢, O. (1916). "Zm' Terminotogie des pfla.nzlichen Generatfio~tswechscls." Biol. Zbl. 36, 337. ~OSJ~N~n~¢Cl, O. (1917). "Die ~edukgions~bcilung und ihre Dege:aeralfion in Hiera.- cium." Svensk hot. Tidslcr. ii, 1~5. (1930). "Apogamie und Pari)henogencse bci Pfla~zen." Hdb. de,r Vererb. 2, 1. Berlin. Se~sra~, t(. (1929), "Embryologie dcr A~Niospermcit." Hdb. el. Pflco~zc~a, uat. 2 (2). Berlin. S:pr~r~c4nr¢, E. (I935). "Uber apoga.me (vcgclialfiv en~s~a,ndene) Sporogone an der bivalcnten P, asse des Laubmooses Phascu.m. c.uspidatu.m." Z. "b~dulc! A hslam,m., u. VererbLeh,re, 69, 2~t9. S'rmi r n:xs, W. C. (]898). "l]-ber Cln'omosomenteilmtg bci der Sporenbildung der ]r~rne." Be'r. dl,sch,. bot, Ges. &6, 261.. STr~,~.s~m~o]~:g, E. (]910). "Sexuclle mtd apogamc ]~%rgpflanzung bei Ur~bicacecn. '' Jb. wiss. Bot. 47, 245. T2(C~CHOL~.~, G. (1922). "Zytologische Sgudien iiber die Ga,ggung 2~os(~." Actc~, Hort. be~.g. 7, 97. Ws'r'vsTnr~, lP. v. (192~t). "Morphologie und Physiologic des Formwcchsels der 5~oose auf. genclJschc C~rtmdlage." Z. i'ndukt. Absta,m,m.- ~. gererbLehre, 33, 1. --(1928a). "Norphologie trod Physiologic des Formwechsels der Moose ~mf genel~ische G rul~dla.gc. Ill." Bibl. get,at., Lpz., 10, 1. ,J'onrn. of ~o~el,ics xxxll 15 228 Inheritance of A1)o81)ory in Soolopendrimn vulgate

Wm"rsT~t~, F. v. (1928 b). "Ubor l~lasmagisehe Verorbung trod libra, d~s Zus~ml- menwh'kon yon Gonen und Plasma." Bet. dtsch, bet. Ges. 46 (32). WrNc, e, O. (1917). "The chromosomes." C.R. Lab. Carlsbe~r(/, i3, I3I. WII~ICL~I~, }I. (1920). Verbreitung wnd U,rsache der Parthenogenese im P flanzen- w.d 2'ierreich. Jena.

EXPLANATION OF PLATES Vl--Xll

PL*TE VI Transparencies of young fronds of young plants o[" ghe peculiar, showing galnetophylae gissue, and in Figs. 1 trod 4 venagion. Figs. 1 and 2, x 7; Figs. 3 and 4, × 3.

Pr, a~'~ VII Figs. 5-11. Successive fronds of young plangs of ghe peculiar, showing beginlfing of game6ophygic ouggrowgh and rhizoids, x 2-4. Figs. 12 and 13. Fronds wigh gamegophygie ouggrowgh thrgller cleveloped, x I~.

I'LA'r~ VIII Figs. 14--19. Various gypes of fronds of peculial'S, nag. size. Fig. 18 x l{. Fig. 20. Fronds of young normM sporophyge, a--d slighgly enlarged, e nag. size.

I'r~AT~ IX Figs. 21-23. Peculiar spol'ophyges. Fig. 24. NorlnM sporopllyge. PsA'r]s X

Figs. 25, 26. Fronds of fully grown sporopllyges of ghe variegy c.rispnm muricat,t .m, x -}. Fig. 27. Frond of fully grown SpOl'Ophyge of ghe variegy 8agillal,lum, '7)rqjecl,um,× J~. Fig. 28. Frolld of fully grown sporophyge of vulga,re gype, x,!r. PL,t~'~ XI Fig. 29. Edge of leaf of a peculiar sporophyge, × 90. Fig. 30. Edge of leaf of norlnM sporophyge, x 90. Fig. 31. Base of frond (begween ghe veins) of fully grown fl'ond of the peculiar SpOl'O- phyge, x 90. Fig. 32. Base of frond (begween ghe veillS) of normM, corresponding go Fig. 31, x 90. I'SAT~ XII Figs. 33, 84. Sporangia congMning sperlnagozoids, x 1800. Fig. 35. Sporallgium containing spores, x 1800. Fig. 30. 8permagozoids in a sporangiuln, x 4-200. Fig. av. 8porangium wigh spermagozoids, x 1800. Fig. 38. Angheridium wigh spertnagozoids, x 4:000. All magnifieagions ~re approxim~ge JOURNAL OF GENETICS, VOL. XXXII, NO. 2 PLATE Vl

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