SHORT TITLE TAXONOMY OF ZYGNEMACEAE. by Alauddin Ahmad

Transcription

1 SHORT TITLE TAXONOMY OF ZYGNEMACEAE by Alauddin Ahmad

2 MORPHOLOOlCAL AND TAXONOMIe STUDms IN CULTURE OF SOME IiwIÂN ZYGNEMACEAE Alauddin Ahmad A thesis submitted to the Faculty of Graduate Studies and Research in partial fultilment of the requirements for the degree of Doctor of Philosophy Department of Botany, McGill University, Montreal. July 1968 ~ A1auddin Ahmad 1969

3 MORPHOLOOlCAL AND TAXONOMIC STUDIES IN CULTURE ON SOME INDIAN ZYGNEMACEAE BI Alauddin Ahmad ABSTRACT Twenty-four strains of Zygnemaceae, belonging to four genera (8 species of Spirogyra, 4 of Zygnema, 2 of Mougeotia and the new species Lloydiella kankensis ), were isolated from soil-samples collected in Bihar state of India. The vegetative morphology, process of conjugation and development and germination of asexual spores were studied in detail under controlled environmental conditions. A new member of the fami~, Lloyd1ella kankensis, and a new species of ZYgnema, ~. ramosum, are described. On the basis of the cultural studies on variations anâ stabil1ty of some of the morphological and reproductive features of these 15 species of the Zygnemaceae, the taxonomic criteria used in delimiting the genera and species of the family are reassessed and re-9valuated, some new criteria and lines of further research are suggested.

4 TABLE OF CONTENTS INTRODUCTION MATERIALS AND METRODS A. Isolation or Strains B. Cul turing Conditions C. Mating Technique D. Photographs E. Note RESULTS Lloydiella gen..!!2!. LIoydiella kankensis.!œ. ~. Zygnema Agardh ZYgnema sterile Transeau Zygnema ramosum!2.!!2!. Zygnema spontaneum Nordstedt Zygnema extenue Jao MOugeotia Agardh Mougeotia angoiensis W. & G.S. West Mougeoti. scalaris Hassaii Spirogyr& Link Spirogyra juergensii Kuetzing Spirogyra gracilis (Hassall) Kuetzing Spirogyra retlexa Transeau Spirogyra condensata (Vaucher) Kuetzing Spirogyra Iiana Transeau

5 SpirOgyra pratenei! Transeau 47 Spirowa hyalina Clave 50 Spirogyra irregularis Naeg.li 52 DISCUSSION AND CONCLUSION 56 SUMMARY 64 LITERlTURE CITED 65 APPENDIX l 69

6 ACKNOWLEDGEMENTS The writer wishes to express his sincere appreciation and gratitude to Dr. M. E. Goldstein for the constructive criticism and advice willingly given throughout the period of research and writing; to Drs. R. Sattler and K. Maier and Miss. V. Schatz for their assisstance in translating German" literatures, to Miss. Fauzia Sudeki for Japanese and to Mr. T.H.Hassell for Spanish literatures; to members of the Faculty and fellow graduate students for suggestions and encouragement; to Dr. Hannah Croasdale for the preparation of Latin diagnoses; and to bis friends'is.s. Jaurihar for sending the soi1," samples, and A.F. Muhammed, K. Howard and D. Lapointe for their help during the period of writing. Dr. M.E. Go1dstein received a grant from the National Research Counci1 of Canada during the course of this st~, this support is gratefu1ly acknow1edged.

7 1 INTRODUCTION The til.amentous green algae ot the tamily Zygnemaceae are among the most oommon species to be f'ound in f'r.sh vater habitats aroudd the world. Since the development ot the microscope their abundance has attraoted ~ naturalists am botaniste and. one f'inds a _81th ot publications in the literature conoerning the morphology and taxon~ of' this group ot organisme. This li terature has been more than adequately discussed by Transeau (1951), Randhawa (19.59), and Gauthier-Lime (196.5), au of' wjlom have published l1lonographs on the Zygnemaoeae. It is clear trom their reviews ot the li tersture that a oonsiderable amount ot debate oocurrèd vith regards to taxonomic criteria used to delimit genera and. species :(Czurda, 1932: Fritsch, 1935; Transeau, 1934, 19.51: Smith 1950). However, in 1951 Transeau, who devoted a great deal ot his research career to the study ot the Zygnemaceae, published the f'irst, def'initive monograph ot the tamily. The Most notable ach1evement of' this monograph vas the tirst clear taxonomie delimitation ot genera based primarily on chloroplast structure and aspects ot the conjugation procges. As a consequence he recognized 13 genera. However, at the species level, partioularly tor species of' Spirogyra, Zygll$l1la" and!1ougeotia, the limits vere not clearly def'ined. He more clearly def'ined the taxonomie criteria to be used at the species level, such as, dimensions ot vegetative cells, zygospores, and aplanospores, wal1 s~~~cture and shape ot sexual and asexual resistant spores, and the detaile of conjugation process, but bis utilization of these criteria, particularly cel1 dimensions, vas neither o consistent nor Adequate to delimit many species. In the more recent monographie treatments of' the family by Randhawa (1959) and Gauthier-Li~vre (1965) little or no improvement in the delimitatior, of species was made, and

8 2 in some cases more contusion was added, particularly by the description of new species. According to Transeau (1951) there are 13 genera and 534 species in the fami1y Zygnemaceae. Sinee the publication of his monograph two new genera, Mougeotie11a and Neozygnema (Yamagishi, 1963b), and sorne 90 new species have been described, thus bringing the total of 15 genera and 624 species (Caballero, 1947; Marga1ef, 1951, 1952; Woodhead and Tweed, 1955; A1eem, 1961; Das, 1962; Nipkow, 1962; Kamat, 1962; Yamagishi, 1963a, 1963b; Gauthier-Li~vre, 1965; and Mueller, 1966). It is apparent fram the abave monographie treatments that short term observations on naturally occurring populations or the use of preserved material 1imited the ability of previous investigators to assess the reliabi1ity of taxonomie criteria in the Zygnemaceae. However, in light of modern culture techniques the phycologist can now st~ unialgal or c1ona1 populations over a ~ long period of time under known environmenta1 conditions to hetter eva1uate characteristics as taxonomie criteria. Such studies have proved to he of decided value in understanding the taxonomy of certain genera such as Ch1amydOMonas (Gerlorf, 1940; Ettl, 1959), C10sterium (Cook, 1962), Gonium (Stein, 1959) and Eudorina (Go1dstein, 1963). In the case of the Zygnemaceae in which the conjugation process is often essential for species identification, yet in nature, it is generally ephemera1 and often seasonal, long term studies in culture would prove Most valuab1e. At present only a very few cultural studies on species in this family have baen made, (Allen, 1958; Geit1er, 1958; Hoshaw, 1965). Allen was able to show that variation in cell dimensions and numbar of chloroplasts per ce11 occurred within a clone. Similarly, Geit1er's description of MOugeotia heterogama and Hoshaw's description of the life history of Sirogonium melanosporum give a much batter understanding of the reproductive process in

9 :3 tbese organt liiui. ~. '; '. DuriDg the lut :3 years 24 clones ot Zygnemaceae wre 1.olated :rrc semples colilected in B1h&r, IDdia. Initial attempts to ident1tj' these clones utu1sidg the IlODograph:: of Transeau (19.51) general.l7 proved UIlSUCce.stul. Theretore, the t1rst major a1a of th1. st~ wu to e&n7 out a c:letaued. inve.tigation on the vegetative structure ad reproductive processes ot the clones UDder controlled env1rcmmental CpDd1 tiona. Bued. on tb1s study, the.eccmd. IIl&jor objective vas to utilise the Ilost rel1able vegetative and. reproductive characters in the rev1s1on of ex1.st1ng speo1e. descriptions and. to describe new spec1es, 1t nece.s&ry. e

10 4 MATERIALS AND METRODS A. Isolation of Strains The tventy-four strains or clones of Zygnemaceae belonging to four genera utilized in this st~, were isolated tram soil samples coilected in Bihar state of India (Appendix I). These soil samples vere collected!rom rice fields, mlddy edges of ponds and loikes, and wet low-lying araas, in Ranohi, Kanke, Jona Falls, Hundru Falls, and Daltongunj. Except for Daltongunj, ail the coilecting sites are within a 25 miles radius of Ranchi. Ranch! is situated at ' N latitlde and ' E longitude at an altitude of 2100' above sea level (Jha, 1965). The climate ia of subtropical type w1 th a hot and wet season frem June to September (Srivastava, 1964). It is during these months, that the members ot Zygnemaceae grow Most luxuriantly. The climate of Kanke, Jona and Hundru Falls, and Daltongunj is ~ not much ditferent than that ot Ranchi. The mud samples were air-dried for at least 2 weeks, then packaged and shipped by air mail to Montreal. Upon receipt ot the samples, a teaspoon of soil was placed in a sterile petri dish ar~ rewetted with sterile distilled wa ter. If resistant spores of Zygnemaceae were present, germlings would appear in 4-7 days. Very often these germlings differed in width of vegetative cells and number of chloroplasts per celle Ten clones of each type were isolated fram each soil sample. The clones were isolated with the help of a fine glass pipette under a dissecting microspcope and placed in a watch glass containing sterile distilled wa ter. After several washings single gennlings were placed in tubes of Pringsheim's soil-water medium without Caco 3 (Starr, 1964). The tubes were placed under illumination of 300 ft.-c. intensity at 20 0 C. Good vegetative growth was usually achieved

11 5 in 305 weeks, and sinee a11,clones proved to he homothallic, conjugation was generally observed 6-8 weeks after inoculation. B. Culture Conditions Experimental work and maintenance of cultures were carried out under controlled environmental conditions. The tempe rature of the culture poom was maintained at 20 0 t 2 0 C. The light source was banks of cool-white standard fluorescent tubes, automatically controlled to give 16 hours light and 8 hours dark, daily. The strains were maintained in ~ pint milk bottles of soil-water maedium. The strains were transferred into new bottles every 4-5 weeks. Newly transferred strains were allowed to remain in bright light ( ft.-c. intensity) for 3-5 weeks and then were removed to a place of lower light intensity ( ft.-c.). No attempts were made to make these clones bacteria free. AlI the experiments were carrieci out in soil-water medium. C. Mating Techniques The basic technique employed was that used by Allen (19.58) for the induction of sexual reproduction in SpirogYra. Sterilized 1.5 % agar in distilled water was poured in sterile petri dishes. When the agar was solid, filaments were removed from 2-4 week old stock culture with a glass pipette and placed on the agar surface. The excess soil-water was pipetted off and the agar plates were placed under illumination of ft.-c. intensisty. Conjugation tubes were generally formed within 2-3 days. In addition, modifications of the Allen technique were also amployed. The agar surface was replaced by filter paper or cheese clotho Deep petri dishes were partially filled with distilled water or soil-water

12 6 supernatant, and small petri dishes ven placed in the solution. rilter paper or oheese oloth vas plaoed over the smau petri dish in such a vay tbat the edges of the paper or cloth WN bnersed in the vater &Dd thu the surfaoe vas kept mo!st by' oapillary' action. As in the AUen technique, filaments W9N plaoed on the moist surfaoe, the dishes 1181"8 placed in bright l1ght and conjugation oommenoed in 2-3 days. Further moditications of this technique eould be made using cheese eloth ta determ!ne the influence of' exposure or tm.ersion in the soil-vater on the oonjugation prooess. Dishes an set up as indioated. for controls. In other set-ups the filaments ore plaeee! imd..r<,tlie;!~"').eloth over an inverted smau petri dish. The vater in the deep dish vas raised to diffennt levels so the filaments an Just at the meniseus or submerged to varying degrees. In au cases only the filaments in the control setup and those at the menisous under--vent oonjugation, while the filaments in other setups remained vegetative for a oek or more or until evaporation brought vater level below the surfaoe of the small petri dishes. D. Photographe Photographs vere taken vith a Kodak 3.5 mm~ camera vith eleotromagnetic shutter coupledvith a Vicker Exposure Unit. Most photographs vere taken vi th Kodak Plua X film though in SOllle oases Kodak High Contrast Copy film was used. E. ~: Descriptions of new species have been sent ta Dr. Hannah Croasdale for the preparation of Latin diagno s. These diagnoses will be appended to the thesis when received.

13 1 RESULTS LLOIDIELIA, gen. nov. (fig. 1-6 ) Unbranched f'i1aments; uture vegetative.cells vith 2 ribbon-l1ke axile chlorop1asts, each vith severaj. scattered pyrenoids; p1astids connected wi th a cytop1asmic bridge conta1n1ng nucleus.. 4-" Conjugation sca1arif'orm, anisogamous; entire protoplast5 of' gametangia serve as gametes, thus no cytop1asmic residue 1ef't in the gametangia; the walls between the conjugating gametangia partially disso1ved to f'orm a small pore through which the male' gamet. mgrates; zygotes f'ormed in the f'em&le gametangia and not enc10sed in ~Sporang1a". LLOIDIELIA KANIŒNSIS, sp. nov. (f'ig. 1;.;6) Mature vegetative cells long and. narrow, 19-23)1 wid4t and 14O-215}1 long, with 2 ribbon-l1ke axile chloroplasts, connected by a cytoplasmic bridge contain1ng nucleus; plastids wi th several pyrenoids; chloroplasts occupy almost the who1e length of' the call except a small portion on one em of' the ceu where the vacuole i8 evident. Conjugation scalariform, anisogamous, homothal11c, dioec1ous; male f'ilaments fragment into 1- or 2-celled (rarely me.ny-celled) pieces; feule f'ilaments remain intact; developing f'ema1e gametangia longer than the male gametangia and show conspicuous unilateral swel11ng prior to contact with the male; male gametangia geniculate bef'ore contact w1 th f'emale; no conjugation tube f'ormed; enure protoplast of' the male gametangium mgrates into the f'emale gametangium tbrough a sma1l pore f'ormed between adjacent valls of' the conjugating gametangia; zygote f'ormed in the f'emale gametangium am not enclosed in "Sporangium"; zygospores spherical to ovoid, bounded by single wall lapr; wall SlIlOOth and yellowish in color. GEOORAPHICAL DISTRIBUTION STRAIN: 304. Kanke (Bihar) India. This nev enti ty (Llo@ella kankensis) described abave vas isolated f'ram soil samples co1lected f'ram a rice f'ield in Kanke, India. The description of' its vegetative morphology am the process of' conjugation i8 based on observations of' a clonal culture (strain 304) studied under controlled enviromental e conditions. With respect to vegetative 1Il0rphology, it vas f'ound that recently' divided cells of' Lloydialla kankensis are ahost identical to mature vegetative cells of' Most Mougeotia spec1es (f'ig. 2). These cells contain a single plate-

14 8 8 Lloydiella kankensis Jœ.!!2!~. Fig. 1. Mature vegetative oeu of strain 304. Note the clear cytoplasme bridge between the two plï.stids. X 45 Fig. 2. A young ceu wi th only one chloroplast in protile view. Note the nucleus appressed to the plastid. X 125 Fig. 3. Early stage in scalaritorm conjugation. Note one-oelled male gametangia and the swollen temale gametangia. X 50 Fig. 4. Cells ot temale gamet&ngia undergoing ditterentiation even betore coming in contact with the the male gametangia. X 50 Fig. 5. Late stage in soalariform oonjugation.,1 50 Fig. 6. Late stage in scalaritorm oonjugation. Note the zygote in the :t"emale gametangium. and the gametl:.ngia wi thout any cytoplasme residue lett. X 50

15 f~1 \0

16 9 lib axile chloroplast vith aeveral scattered. pyrenô1ds. The nucleus ia located in the center of the oell to one side of the chloroplast. As the ceu matures, it elongates and the ohloroplast divides into two. Fo11owing division, the nucleus 1s found in the cytoplasmic bridge betveen the two chloroplasts (fig. 1). The conjugation is scalarif'orm, hol1oth.uic and dioec4oua. It undergoes sexual reproduction easuy both in soil-water bottles as vell as on Agar plates. In soil-water bottles zygotes are formed 8-10 veeks after subculturing, whereas, a 3-week old culture placeci on agar plates initiates conjugation in 2-3 days and zygotes are formed in 4-6 days. Vegetative filaments are indistinguishable until the proc8ss of conjugation i8 initiated. The male filaments can he distinguished because they break up into smau segments containing 1- or 2-ce11s, and very rarely more than this number (fig. ;J). The male gametangia undergo geniculation even before they make contact vith the female filaments. At this time, the female filaments generally remain intact and the cells are usually noticeably longer than those of the male filaments. The developing female gametangia then svèll considerably, particularl:y on the side which will come in contact vi th the male gametangium. When contact is made,a conjugation tube is not formeci by either gametangia. Whey are attached directly. A small pore is formed in the wall where the two gametangia meet. The entire protoplast of the two gametangia form the two gametes. The male gamete then passes through the narrow pore into the female gametangium (fig. 5) and fuses with the famale gamete which lies in the swollen portion of i ts gamet&ngium. Fo11oving gamete fusion the zygote i8 :!ormed which is spherical to ovoid in shape and is bounded by a single SMOOth ct yeuowish wall. No cytoplasmic residue is left in ei ther gametangia after the zygote is :!ormed. The zygote lies in the female gametangium (fig. 6).

17 10.e No septa are laid down to segregate that portion ot the temale gametangium containing the zygote tram the rest ot the temale gametangium. In other words. zygote is not enclosed in a "sporangium". Four ot the 13 genera (namely, Mougeotiopsis, Debarza, Mougeotia, and Temnogametum) recognized in the tamily Zygnemaceae by Transeau (19.51), Randhawa (19.59), Yamagishi (196Jb) and Gauthier-Li~vre (196.5) have cells with a single axile plate-like chloroplast. These 4 genera ditter tram each other in having chloroplasts wi th or wi thout pyrenoids and. in the details ot conjugation process (Tabla I}. The morphology ot the chloroplast in these genera is considered by Czurda (1932) to he so similar that he puts them together in one genus Mougeotia. However, ~ phycologists (Fritsch, 193.5; Transeau, 1934; 19.51; Smith, 19.50; lyenger, 19.58; Randhawa, 19.59; Gauthier-Lime, 196.5) believe that the details ot conjugation are so distinct that they are not only ot taxonomic but of phylogenetic importance ~ ~;ugeotiopsis, is distinct trom other genera in having a chlorapiast without pyrenoids. In addition, the zygote is not separated trolll the gametangia by septa. Debarya, is also distinct from other genera in having the entire cqntents ot the two gametangia participating in the tormation ot the zygospore. In addition, the gametangia become tilled vith successive layers ot pectic and cellulose colloids as the gametes move into the conjugatiol". tube. Temnogametum, is distinct in having special gametangial cells cut ott trom the vegetative cells. No cytoplasmic residue is lett and the zygote is not separated trolll the gametangia by septa (Transeau, 1932). Most species ot Mougeotia have a single chloroplast with pyrenoids. Some cytoplasmic residue is lett in the gametangia and the zygospores are separated tram each gametangium by one or two septa (Transeau, 1926, 19.51).

18 - 1 fi TABLE 1. Comparison o.f l1embers of -che ilyënelhaceae With Axile Plate-like Chloroplasts. Humber of Chloroplast;:,. Harked Pbysiological Anisogamy. Special gametangia.l cells. Pectic-cellulose colloidal material in the gametangia. Cytoplasillic residue in the gametangia. l'!ougeotiopsis Debarya Tellw.ogametum Hougeotia ivlougeotiella, Lloyct(ella, Pa.Lla, ld94. w1t~rock, West, W &G.b. Agardh, Yamagishi, gen. ~. 10'1 "1 d97. 1 (j (;-a~ly 2?) - (+?) Septum separating the zygote froid rest of gametangia Co~ugation pore - Legends: + = present, = absent. + + "". """,

19 11 In other words, the zygospore is al ways eno1osed. wi thin a "sporangium". This character of having a septum separating the gametangium from the portion'" containing the zygospore, in other words, of the formation of a special structure Il sporangium", is considered. to be of phy10genetic as well as taxonclllic importanoe. Fritsch (193.5) oonsiders it as an eto1utionarily advm"ë(lf'ea.t~, whereu, Cha.d.efaud (1963) as a priddtive characteristio. A careful look at the descriptions of species of Kougeotia in the two monographs b,y Transeau (19.51) Randhawa (19.59), revea1s that there are Dine species, in which the zygospore is not eno1osed in a sporangium. But neither of the Aboye mentioned. authorshas mentioned this fact in their general description ot the genus, 41though they have been caretul enough to mention the exceptions of two chlorop14sfs and. anisogamy. Yamagishi (1963) separated these Dine species into a naw genus Mougeotie11a. In this genus the zygospore is not separated trom the gametangia am some cytoplasmic residue is &lways left after the tubioll' O,t. the gametes. Thus the only feature that distinguishes Mougeotiella tram MOugeotia is the absence ot a septum between the conjugation tube and the gametangia. Since this has been regarded as an important phylogenetic and taxonomic character, the present author tee1s that these 9 spacies should be regarded as separate entity. The new genus Lloydiella is distinct from other genera in having two chloroplasts par cell at maturity, distirjct anisogamy, and. the tormation of a smal1 pore in the reglon ot contact between gametangia. In addition, there i5 no cytop1asmic residue 1eft in the gametangia and. the zygote is not enc10sed in a "sporangium". Three species of Mougeotia (!:l. transeaut,!:l. fioridana and. H. poinciana) are reported to have anisogamous conjugation. The details of oonjugation in these species are lacking. The only evidence of anisogamy appears to he the position ot zygospore, which is formed in the space between the 'temale'

20 12 gametaïlgium and the conjugation tube. In LloJdiella, there is no conjugation tube and only a portion ot the spetulll 18 dissolved torming a small pore in the septum between the two gamet&ngia. The two gamet&ngia dif'ter in size and shape. The male gamete is clearly seen to pass through the smau pore into the swollen temale gametangium. The zygote is tormed entinly in the temale gametangium, thus, in LloJdiella, conjugation is markedly anisogamous. Thus the new genus Llo1diella is distinct trom. the reat ot the tive genera vith axile chloroplasts, in having two chloroplasts per cell, no cytoplasmic residue lett in the gametangia, marked anisogamy, no separate sporangia and in having a SlIlaU 'conjugation pore'. ZYGNEMA Â~~rdh, Globulina Link (1820); Tendaridea Bory ( ); SteUu1ina L1nk (1833); Thwaitesia Montagne (1838); Tm:laridea HassaU (1868); ZuogoniUlll Kuetzing (1843); ~ Bory z. T. Grunow (1868); and Pyxispora West, W. & G. s. (1897). Filaments usually unbranched, sometimes branched, vith short cylindric ceus; vegetative cells 1-9 times as 11ng as broad, vith 2 stellate chloroplasts, each vi th one pyrenoid; a single nucleus in the cytoplasmic bridge between the two plastids. Asexual reproduction by ôkinetes and aplanospores. Conjugation scalariform and, or lateral; zygospores tormed either wholly in the conjugation tube or in one ot the gametangia; zygospore variable in shape, compressed-globose to ovoid, with three-layered wall, outer and inner th1n and hyaline, the middle thick, variously ornamented or SlIlOOth, and variously colored. Parthenospores sometimes present, resemble zygospores in wall structure and shape. ZYGNEMA STERILE Transeau, (tig. 7-12) Transeau, Trans. Amer. Microscop. Soc. 53: 212, and 1951, The Zygnemataceae, Ohio state University Press, Columbus. p , Pl. VII, tige 11. Skuja, A Hedvigia. 77: 54,Pl. II, tige 4. Randhawa, M.S Proc. Indian Acad. Sci. Sec. B. 8: 150, tige 30. and 1959, The Zygnemaceae, Indian Council ot Agricu.ltUl'al Research, New Delhi. p , tige 228. Filaments unbranched; vegetative cells p broad and )1 long, vith 2 stellate chloroplasts;,cellwall d-!_variable thickness; nucleus in the cytoplasmic bridge between the two plastids; each plastid vith one small pyrenoid.

21 13 13 Zygnema sterile Transeau Fig. 7. A vegetative celle X 265 Fig. S.filament with all the cell transformed into akinetes. X 100 Fig. ~ A single akinete. Note the double-layered wall. X 265 Fig. 10. Early stage in germination of akinete. Note the swollen outer wall. X 150 Fig. 11. Late stage in germination of akinete. Note young filament and the broken mother cell wall. X 150 Fig. 12. Late stage in the germination of akinete. X 150

22 8 11

23 -.,.1 1"..1 j' '.. l~~ , 7 P'".' ~

24 14 Conjugation not lmown; reproduction by akinetes only; aldnetes thickwaued; wall 2';'layered., hyaline; akinetes p. vide. GEOORAPHICAL DISTRIBUTION STRAIN: 107. Indi. - U.P. and Bihar (Randhawa, 1959) U.S.A. (Transeau, 1951); Graece, Asia Minor (Skuja, 1937). The vegetative cells or strain 107 look very much like those or ~ other species or Zygnema. They are thin-walled vith 2 stallate chloroplasts betwaen which lies the single nualeus in a cytoplasmic bridge.(rig. 7). Aldnetes are formed both in soil-water bottles as wall as on agar plates. In soil-water bottles akinetes are formed 7-10 weeks &tter subculturing and on agar plates, a 4-5 week old culture rdrms akinetes in 5-8 days. Akinete formation generally occurs in recently divided cells as ind1cated. by the reduced length of the cells as compared to mature vegetative cells. The dirrerentiation or the vegetative cell into an akinete is a graduai process beginning wi th an incraase in thickness of the double layered. oeil wall, primarily or the inner layer and the accumulation or starch granules in the cytoplasm. As ind1cated above, the early stages in developing akinetes rasemble vegetative cells except ror the ract that the walls bave increased in thicy~ess and the star-shaped plastids appear more dense due primarily to starch accumulation (fig. 8). At maturity, the aldnetes possess a hyaline double-layered cell wall. The protoplast is brownish-green in color containing 2 plastids which ar~irregular to stellate in appearance and are surrounded by a dense accumulation or starch grains (fig. 9). Though akinete germination vas observed by Transeau (1951) the description of the process vas never published. In strain 107, akinete germination occurs.!!!~. The rirst indication of germination is the swelling

25 1S and. eventually af'rem'ascenoe ot the out.er wau (tig. 10). Follcw1ng the expansion or the outer wall, the oeu enolosed in the irmer wall elongates am then um.ergoes rapid ceu division, torming an int8rcala17 unbranched tila Ment (tig ). The cells ot this nev filament then revert to the typical vegetative charact8r. In general, the morphology of strain 107 Agrees vith the description of ZYgnema sterile exeept for the fact that vegetative cells in strain 107 laok heavy walls. Transeau, based on his observations (1934, 1951), as well as those of Skuja (1937), insista that heavy walls are a consistent feature of vegetative cells of this species. In light of the difference between strain 107 and. the type material of!. sterile, the author had the option of recognizing this strain as a distinct species or variety, but it became olear that the early stages in akinete formation resemble the "vegetative cells" of Transeau. It is therefore felt that the obervations made by Transeau and. Skuja on natural populations of!. sterile vere at a tinte when the specimens vere producing aldnetes, and sinoe eve17 vegetative cell generally differentiates into an akinete, the vegetative cells were not observed. However, until additional strains of this species ean he studied, the species description has been amended to include forms vith thin and heavy vegetative cell valls. ZIGNEMA RAMOSUM!E..!!2!. (fig ) Filaments usually unbranched, sometimes branehed; vegetative ceus ~ vide and )llong, vith 2 stellate plastid per cell; eaeh plastid vith a single large pyrenoid. Conjugation not knowd; reproduction by aplanospores on1y; spores cylindric, thick-walled, occupy the whole sporangium, vith 3 wall layers; outer wall thick, blue, sorobiculate, cylindric; Middle and inner wall thin, hyaline and cylindric-ovoid; sometimes small'intercellular' spaces occur between the outer and Middle valls in the corners; Middle and inner valls olosely adjacent; Middle wall smooth; inner wall granula te

26 16 Zlgnema ramosum J?. l!2!. Fig. 13. A filament with vegetative cella. X 210 Fig. 14. Fig. 15. Fig. 16 iarly stage in the germinationoof aplanospore. Note the outer wall or aplanoaporea breaking up as circular lids. X 125 Early stage in germination. Note the irregular breaking of aplanospore wall. X 125 A young gennling coming out of the aplanospore. X 210 ~!

27 '. ~, () (1...' i'-' 13 1,r- I i' /./ 15 st> 1 j;;" l~

28 () ( / 14.. ~~ "! 1 la 15 R 1" (.

29 17 GEOORAPHICAL DISTRIBUTION Bihar, India (Ranchi, Kanke, and Horhap). STRAINS: 101, 102, 104, and 106. When this new species was first studied it appeared to be MoSt aimilar to two previously described species, Zygnema frigidum and!. giganteum. However, baaed on the original descriptions of these two species (~aft, 1934; Randhawa, 1936) and subsequent descriptions qy Randhawa (1959), it appears that!. ramosum is distinctly different fram these speciea with respect to the number and/or arrangement of cell wall layers of the aplano,pore. As indicated above, there are 3 wall layera in!. ramosum, the outer of which ia thick, scrobiculate and blue, while the Middle and inner layers are thin and hyaline, the Middle smooth and the inner granulate or punctate. In contraàt,!. frigidum has outer and inner wall" thin, smooth and. hyaline and middle wall thick, acrobiculate and blue at maturity. The original description of the spore walls'of!. giganteum is samewhat vague (Randhawa, 1936). Randhawa (1936) states that 2 walls occur, an outer wall which is thick, undulate and yellowishbrown, and. an itmer wall which is thin and granulate. On the other hand, Transeau (1951) after exami~ the material of ~. giganteum collected by Randhawa states that the spore has 4 wall layers, an outer smooth, hyaline wall, and a double-layered mesospore wall. Which ever interpretation of the spore wall structure is correct for!. giganteum, it appears clear that this species as weil as!. frigidum are distinct from newly described!. rame.ua. In~. ramosum, as in!. frigidum, aplanospores seem to bë the only method of reproduction. These strains were mixed together but did not form any zygotes. These strains ~orm aplanospores readily both in soil-water bottles as well as on agar plates. In the bottles, spore formation starts 8-10 weeks after subculturing, whereas, a 3-4 week old culture forma aplanospores on agar

30 18 ZYgnema ramosum (continued) Fig. 17. Early stage in th& germination of aplanospore. Note a young germling caming out after breaking the outer and Middle wall. X 210 Fig. 18. Late stage in germination. Note a young filament with 3 cells. X 150 Fig. 19. A young filament showing branching. Note old aplanosporangia. X 100

31 19 plates in 5-7 days. Almost êver,y vegetative 0811 can function as an aplanosporangium (fig. 13). At the start of aplanospore formation, the cells are fuled vith a large amount of reserved food &nd more starch granules collect around the pyrenoids, which consequently look much larger (fig. 19). Following tbis, a very thick wall is formed around the protoplast which is inside and adjacent to the sporangium wall. This new wall i8 scrobiculate or undulate and. yellowishbrown in color at first, but turns blue in the mature spores. Following the formation of the outer wall, the protoplast contracts slightly and two more walls are formed internai to the the thick outer wall. These two walls are thin and hyaline and. are appressed to one another. The middle layer is smooth and. the inner granula te or punctate. Usually, there are 'intercellular' spaces between the outer and. the Middle layers. The outer wall is always cylirxiric, whereas the two inner walls are usually cylindric-ovoid to ellipsoidal. Aplanospores germinate readily when transferred to fresh soil-water medium in 7-10 days. There is no definite line of dehiscen08 in these strains (fig ). The protoplast may : came out as a germling enclosed within both the Middle and. inner walls, leaving behind the thick outer wall inside the sporangium (fig. 14, 16). Or the whole aplanospore mayemerge fram the ruptured aplanosporangium (fig. 15, 17), then the thick wall ruptures and the germling comes out. Rapid ce Il division occurs in the l-08lled germling, resulting in an unbranched filament (fig. 18). If the filaments with the aplanospores are left for 2-3 months in the old medium, some of the spores germinate but in a conspicuously different manner. They germinate ~~, forming an intercalar,y germling containing several to many cells which are packed wi th starch grains. This type of germination is similar to that described for akinetes in!. sterile, but uniike the latter or any other species know for Zygnemaceae, some of these newly

32 19 J

33 19 J (. - ".. -.'..

34 20 formed intercalary cells produce lateral branches identical to the main axis and thus can not be regarded as rhizoids (fig. 19). Then, like the parent plant, cells of these small branched fil~~nts will produee aplanospores. This pattern of germination of aplanospores and subsequent development of the germlings appear to be dire.tly related to depletion of nutrients in the soil-water medium, for 'in fresh medium, the spores or 1-celled germlings always emerge from the aplanosporangium and produce unbranched filaments. ZIGNEMA SPONTANEUM Nordstedt, (fig ) Nordstedt, De Algis et Characeis Sandwicensibus, p. 17; Pl. l, fig Kolkwitz &: Krieger, Zygnemales, In: Rabenhorst's Kryptogamen Flora von Deutschland und Schweis. 13, Abt. 2: p. 243; fig , fig Transeau, The Zygnemataceae. p. 41; Pl. VII, fig Randhawa, The Zygnemaceae. p. 53; fig Gauthier-Li~vre, Zygnémacées Africaines. p. 76; Pl. XXI, fig. D. Fil&nlents unbranched; vegetative cells Jl vide and )llong; 2 stellate plastids, wi th a nucleus in the cytoplasmic bridge between the two plastids. Conjugation not known; reproduction by aplanospores (rarely by akinetes 1); aplanospores ovoid to cylindric-ovoid, p vide and 22_;2 }l long: spores with three wall layers, Median wall thick, brown, scrobiculate; pits about 2 }l m:;tiameter, 3-5)l apart; outer and inner walls smooth, hyaline. GEOGRAPHlCAL DISTRIBUTION U. S. A. (T',ranseau, 1951); South Africa (Gauthier-Li~vre, 1965); China, Java, India (Randhawa, 1959). STRAIN: 103. The vegetative cells of strain 103 vere found to he }l vide and }l long. They regularly produced aplanospores both in soil-water b~ttles as weil as on Agar plates. In the bottles, the firet sign of aplanospore formation was seen 6-8 weeks after subculturing. Hovever, 3-4 week old cultures

35 ZYgPema spontaneum Nordstedt Fig. 20. Portion of a vegetative filament. X 120 Fig. 21. Filament with two young aplano,porangia. X 270 Fig. 22. A young and an old fil:ments. Note the heavy wall of the aplanospor8s, and only one chloroplast in the developing aplanospor8s. X 270 Fig. 23. An aplanospore crushed open to show outer thin and mid.dle scrobiculate wall. X 350

36

37 ( o 0!I. " ( 20 ~.' 11.. l' \,.' ';~ \ ~,)'1,~. ~1 1I r... 0(\ '1..,f.JfJ... ), ~'",~ \.l. ' "~ ; #1

38 22 formed aplanospores in 3-5 days on agar plates. The cells forming aplanospores, i.e., the "spl~nosporangia" are usually shorter than the vegetative c~lls, being 26-48)l long in strain 103 (fig ). The average length of the aplanosporangia isag>;r-oximately hau that of the vegetative cells. This indicates that cell division occurs prior to the ditferentiation of aplanosponargium, as well as the fact that a single plastid occurs in these cells as in recently divided vegetative cells. However, in almost every developing aplanospore two plastids vare seen, indicating the completion of cell division. Characteristica~, the tirst indication that a vegetative cell is going to differentiate into an ap1anosporangium is the deve1opmentalashort papil1ar outgrowth of the wall (fig. 22). The function of these outgrowths is not lmown but the origin and development of the,.llae is strild.ngly similar to the formation of conjugation tubes in sexua1 species. At the time when the papi1lae are tormed, the cells May contain a single plastid each, but prior to the formation of tàe aplanospore, the chloroplast divides. Following this, the protoplast contracts and secretes a smooth wall around itselt. Subsequently, two more wall layers are formed within this wall. The middle wall is thick, brown, and scrobicw.ate. Outer and. inner walls are thin and hyaline. The mature aplanospores are ovoid to cylindric-ovoid.,but a large number of these have short papillae-like outgrowth corresponding to the papillae of the aplanosporangial wall. The aplanosporangia are cylindric and not swollen with the exception of the papillae. The germination of aplanospores is 1nitiated by the rupture of the outer and Middle walls and a 1-ce1led germling emerges. This germling is bounded by a thin flexible wall which appears to be the original inner wall of the spore. The cell has two star-shaped plastiœ wi th the nucleus in the cytoplasmic bridge between the plastids. As it emerges, it elongates till

39 23 its length is 3-4 times the width, then rapid CElU division follows, resulting in an unbranched filament. In a11 the available description of this species ~anseau, 1934, 1951; Randhawa, 1959; Gauthier-Li~vre, 1965) it is noted that aplanospore production is the only method of asexual reproduction, excep~, tor one drawing by Transeau (1951, Pl. VII, fig. 5) sh~ng akinetes. The production or akinetes in this speoies has not heen contirmed since, yet Randhawa (1959) and Gauthier Li~vre (1965) have inoluded in monographs of the family Zygnemaceae, the abave mentioned drawing by Transeau. If akinete formation oocurs in this species, i t is probably very rare. Strain 103 has never been found to form akinetes. ZYGNEMA EXTENUE, Jao (fig. 24-~n Jao, Sinensia 6: 568, Pl. l, fig. 8. Transeau, The Zygnemataoeae.p , PI.IV, fig. 12. Randhawa, The Zygnemaoeae. p. 283, fig Gauthier-Li~vre, p. 66, Pl. XVIII, fig. d-d'. Vegetative cells i9-29 Jl vide and }l long, vith 2 stellate plastids; plastid with a single pyrenoid; nucleus in the cytoplasmic bridge between the two plastids. Conjugation scalariform, sometimes lateral; receptive gametangia May or May not he enlarged; zygospores sub-globose, ovoid to oylindrio-avoid, sometimes slightly compressed to very irregular in shape in sc~l~riform conjugation, Jl wide and 26-66}l long; zygospores vith :3 wall layera, outer and inner walls, thin and hyaline, Median wall ye11owish-brown, scrobiculate: pits )l in diameter and 2-3)1 Aparte GEOGRAPHlCAL DISTRIBUTION 1959) China (Jao, 1935): Algeria (Gauthier-Li~vre, 1965): India (Randhawa, STRAIN: 105. Vegetative cells cif strain 105' appear to be larger than the cells of the type species. They are p wide and Ju long, whereas, those

40 24 Zlgnema extenua Jao lig. 24. A vegetative cell of strain 105. X 375 Fig. 25. Early stage in scalariformconjugation. X 120 Fig. 26. Late stage in scalar1f'orm conjugation. Note the young zygote with 4 pu.stids. X 150 Fig. 27. A mature zygospore. Note thick scrobiculate middle wall. X 375 Fig. 28. IrreguUr-shaped zygote resul ting from incomplete migration of' the male gamete. X 150 Fig. 29. Lateral conjugation. Note some cytoplasmic residue left in the male gametangium. X 150

41

42 " ( i. cr i,. ~~t..,~ 1! 26 1 \ ) 1! \, J i 1 l 1, l ï ~ ~ i ~ l, " (... 21

43 of the type are p. wide and plong. This probably accounts for the longer mygospores in th1s strain~ S'train 105 reproduces sexually very readily in soil-vater bottles as well as on Agar plates. In soil-vater bottles, it goes sexual in about 7-8 weeks artel' subculturing, whereas a 3-4 week old cultul"e will produce mygospores on Agar plates in 3-5 days. It reproduces more trequently by' scalarlf'orm conjugation but lateral oonjugation is not uncclllllon. DuriDg lateral conjugation, a papilla is fol"jlled in the region of the cross-wall separating two adjacent gametangia. The septum between these two gametangia is stretched considerably towards the projection. A amall pore is rormed in tbis part of the septum through which the male pmete Moves into the female gametangium. Occasion~, a portion of the protoplast is left in the male gametangium but gener~ the entire protoplast (gamete) migrates into the female gametangium and fuses with the female gamete. Following plasmoga MY, a thin smooth wall is secreted around. the zygote (fig. 29). Subsequently, two more valls are formed within this outer wall. The middle wall is thick, scrobiculate, and yellowish-brown. The inner wall is thin, smooth and. hyaline. The matul"e zygospore is cylindric-ovoid, and is generally in contact with the gamet&ngial wall. Scalariform conjugation is initiated by the formation or conjugation tubes by both gametangia and. unlike the type species. no enlargement of the female gametangium was noted. The migration of the male gamete starts soon artel' the intervening wall between the two conjugation tubes is dissolved. The male gamete may migrate completely into the female gametangium, but ve~ often A migration is incomplete (fig & 28). RegardlessJwether migration is <\ complete or incomplete, plasmogamy occurs. If migration is complete, a cylindricovoid zygospore silllilar to those formed in lataral conjugation results (fig. 27~ 25

44 26 However, it the migration ot the male gamete is inoomplete, variqusly shaped zygospores, are tormed whioh reside for the Most part in the temale gametangium and part in the oonjugation tube or it stretohes trom the temale gametangium across the conjugation tube into the male gametangium (tig. 28). The resulting mature zygospore in scalariform,though variable in shape, possesses three wall layers, identical to those described abave tor lateral conjugation lt should be noted that variation in the shape or the zygospore as in strain 105 has been reported by Randhawa (1935) tor!. giganteum, bu.t this species is distinct tram!. extenue on the basis ot wall structure ot the zygospore. MOUGEOTIA Agardh, Conjugata Link (1820); Serpentinaria Gray (1821); AgardhiaGray (1821); Mougeotia Agardhb. (1824); Genutlexa Link (1833); Mesoca~us Hassall (1843); S aerocar us Hassall (1843): stauroc&rpus HassaU (1843; Staurospermum Kuetzing 1 :3; Pleuroc~us Braun (1855); Craterospermum Braun (1855); Pla~iospermUlll Cleve (1868); sïiliâerosyermum Cleve (1868); Gonatonema Wittrock (la7 ) and Debarya Wittrock (1897 Filaments unbranohed; Cells Many times longer than broad, vith plane end walls; chloroplast nat or tvisted, axile, plate-like; nucleus apposed to the cell wall or chloroplast; sometimes two chloroplasts par cell; pyrenoids in one or Many rows. Reproduction by zygospores and or aplanospores; conjugation scalaritom, rarely lateral; isogamous (except threfl spacies); oonjugation tube eut ott tram rest ot the gamet&ngia b,y one or two septa.; cytoplasmic residue lett in the gametangia and aplano,porangia; zygospore usually 'IIlime3-layered wall; Middle wall colorless or variously colored and smooth or ornamented; aplanospores resemble zygospores in shape and details ot wall structure. MOUGEOTIA ANGOLENSIS W. & G.S. West~ (tig ). West, W. & G.S., Jour. Bot. 35: 38. Kolkwitz & Krieger, Zygnemales. In: Rabenhorst's Kryptogamenfiora von Deutschland und der Sohweiz. 13, Abt. II. p. 158, tig. 78. Transeau, The Zygnemataceae, p. 100, Pl. m, tig. 16. Randhawa, The Zygnemaceae, p. 143, fig. 53. Gauthier Li~vre, Zygnémacées Africaines, p. 20, Pl. III, tig. b-b". Vegetative cells22-29 p vide and )U long; one chloroplast par ce11, vi th 4-6 irregularly disposed pyrenoids; chloroplast sometimes tvisted;

45 27 Mougeotia angolensis West, W. & G.S. Fig. 30. A vegetative cell with a large nucleus and twisted chloroplast. X 150 Fig. 31. Nucleus in optical section. Note fat globules around. the peripher,y. X 375 Fig. 32. Nucleus in surface view. X 375 Fig. 33. Early stage in scalariform conjugation. Note geniculation. X 100

46

47 o o i, \,, '"""

48 28 Mopg8otia angolensis West, W. G.S. e Fig. 34. Early- stage in conjugation. Note increas8 in geniculation. X 100 Fig. 35. Scalariform conjugation. Note migration of gametes. X 100 Fig. 36. llate stage in scalariform conjugation. X 100 Fig. 37. Late stage in scalariform conjugation. Note granular cytoplasmic residue. X '.. \

49

50 c'! 1 \ \ 1 \ i i! 36 " 0) '. ('> 0, '. 0

51 29 nucleus adjacent to chloroplast, somet1mes conspicuous, globose or slightly ellipsoidal. Conjugation scalariforlll; fertile cells geniculate: zygospores formed in the conjugation tubes, short cylindric vi th concave sides, varying frolll }l in diameter, spore wall l-1a.,vered, smooth and. yellovish. GEOGRAPHICAL DISTRIBUTION Africa - Angola and Congo (Gauthier-Lime, 1965) India - Bihar. STRAINS: 301, 302, 305 lnd 306. Strain 301 undergoes sexual reproduction in soil-water bottles as vell as on agar plates, but strains 302, 305 and 306 do not.s-trains 302, 305 am 306 very rarely form zygospores in soil.."ater bottles and were never./ observed to undergo conjugation on agar plates. On the other ham, strain 301 t'orms zygotes 5-7 weeks after subculturing in soil water bottles. Similarly, a 3-4 week old culture ot' the 9ame strain, t'orms zygotes on agar plates in 2-3 days. The t'ollowing details ot' conjugation process is based on the observation on strain 301. The conjugation process is initiated vith the contact and slight geniculation ot' the complementary gamet&ngia (t'ig. 33). Gradually, the geniculation ot' the gametangia becomes more pronounced t'orming acute angles (t'ig, 34-35). In most cases, no det'inite conjugation tube is formed. Where it is formed, it is very short, 30-40)l long, and is always t'ormed after the intervening wall ot' the gametangia has dissolved. Upon dissolution of the gametangial valls the undift'erentiated gametes migrate, almost simultaneouàly, towards one another (fig. )6). As migration proceeds, the gametes gradua~ contra ct and then unciergo plasmogam.,y, either in the space between gametangia or in the short conjuagtion tube. A granular cytoplasmic residue is always let't in the gametangia. The zygospores are compact, cylindric and bounded by a single yellowish, smooth wall. The zygospores of the type species are s,118.11,

52 30 whereas both the Congolese (Gauthier-Li~vre, 1965) and the Bihar strains (strain 301) have much larger zygospores. With respect to the shape of zygospores Transeau (1951, p. UW) pointed out "West's drawing might be misleading. The polar ends should be visualized as c1rcular". One of Gauthier-Li~e's two drawings (1965, Pl. III, fig. b') does have circular polar ends. AlI the zygospores examined in the present study have circular or straight polar ends and never conoave as West's drawing suggests. The vegetative cells of all the four strains are identical. The chloroplast regularly shows the type of twisting described for strain 303,!!. scalaris). In addition, the nucle1 are very large and consp1cuous, with a diameter of about half that of the vegetative cell (fig ). The conspicuous nature of these nuclei 1s primarily due to a large number of 'fat' globules lying adjacent to the periphery of the nuclear me.brane (fig ). The exact nature and function of these globules is not lmown. The globules are also present in the peripheral cytoplasm (fig. 30). Neither West (1897) nor Gauthire-Li~vre (1965) noted any peculiarities in the nuclei of the strains they studied. MOUGEOTIA SCALARIS Hassall, Bassall, Ann. & Mag. Nat. Rist. 10; 45. Kolkwitz & Krieger, ZYgllemales. In: Rabenhorst' s Kryptogamentlora von Deutschland und der Schweiz. 13, Abt. II. p. 128, fig Transeau, '1951, The Zygnemat&ceae. p. 93, Pl. XIV, fig Randhaws, The Zygnemaceae. p. 133, fig. 28. Gauthier Li~vre, p. 29, Pl. V, fig. c. Vegetative cells }l wide and }l long; one chloroplast par cell; plastid may be twisted in older (mature) cells, with 4.10 pyrenoids in a roll. Conjugation scalariform, isogamous; fertile cells straight or curved; zygospores formed wolly 1ft the conjugation tube, ovoid to globose, sometimes oblong and irregular, )l in diameter; spo1'8 wall 1-1ayered, yellowishbrown and smooth.

53 31 Mougeotia scalaris Hassall Fig. 38. A vegetative filament with mature cells showing twisting of plastid. X 100 Fig. 39. Yo~,g recently divided cell with flat palstid. X 100 Fig. 40. Young cells with plastids beginning to,~st. X 100

54

55 ! (, 1 i 1 1 r! 1! (

56 32 Mougeotia scalaris Hassall Fig. 41. Early 3cglariform conjugation. Note initiation of.:. conjugation tube and bending of filaments. X 100 Fig. 42. Early scalariform conjugation. X 100 Fig. 42. Late stag9 in scalaritorm conjugation. Note the migration of the gametes and the formation of septum between the conjugation tube and the gametangia. X 100 Fig. 44. Late stage in scalaritorm conjugation. X 100

57

58 j (),-.' :;":'.',>. --;.., ( 42 ( ' j j j j j

59 33 GEOGRAPHIClL DISTRIBUTION U. S. A. (Transeau, 1951); Europe (Kolkw1tz & Krieger, 1944): China; Japan; India (Randhawa, 1959). STRAIN: JOJ. A ver,y distinctive feature of this strain is the twisting of chloroplast (fig. J8). In MOst of the mature cells and in the developing gametangia the entire chloroplast is twisted. The twisting is difterent from that in Spirorqra, In Spirog;yra, the long ribbon-like chloroplaat is spirally arranged. in!rhe preipheral cytoplasm, even immediately after division. However, in strain JOJ, the plastid is always a tlat axile ribbon, at least.just after the call division (fig. J9), and May become progressively twisted on its own axis as the cell elongates (fig. )8). The twisting seems to be caused. by a faster elongation of the plastid than of the cell wall. As a result, the plastid becomes longer than the oell itselt. To accommodate itselt within the cell, the plastid starts twisting fram one or the other or both ends am. gradually procaeds towards the Middle (fig. 40). In older cells, depending on the length of the cell, the plastid May exhibi t 4-12 turne. This phenomenon of twisting of chloroplast is exteremely common in this strain under controlled environmental conditions in soil-water bottles as weil as on Agar plates. Twisting also occurs at elevated temperatures (upto J5 cl. The oocurrence of this phenomenon has not been discussed in the literature, however, Randhawa (1959, p. 47, fig. IV) has a drawing of MOugeotia reflexa exhibiting a twisted chloroplast. strain JOJ undergoes sexual reproduction readily both in soil-water bottles and on agar plates. In soil-water bottles, zygotes are formed 5-7 weeks after subculturing, whereas, on agar plates, a J-4 week old culture forma

60 zygotes in J-4 da.ys. Early stages of conjugation in strain JOJ are difterent than in strain J01 ot H. angolensis. Here, the conjugation tubas are always fomed by one, or by both g8l1letangia, and in some cases a single gametangium may tom two conjugation tubes, even batora two tilaments malee contact. After the initiation ot conjugation tubes, the gametangial cells always geniculate (tig. 41), at the pointswhera '.;..-:;.~'..', the conjugation tubes are tormed and in the direction opposite to the tubes. Geniculation is never as pranounced as in!:l. angolensis.subsequently, the conjugation tubes ot compatible gametangia.. make contact and the walls between the tubes dissolve. In all cases, where two conjugation tubes are tomed by a single gametangium, one is non.tunctional. o~ a portion ot the protoplast o~ the g8l1letangia tunctions as gamete, which migrates into the conjugation tube as unditterentiated protoplast.(fig.42-4j). The migration of the two compatible gametes is not simultaneous (fig. 4J). The contraction of the gametes takes place in the canjugation tube. Plasmogamy occurs in the tube and the zygote is formed. A wall is laid down on each side ot the conjugation tube to separate it tram the rest ot the gametangia. A portion of protoplast is always left behind in the gametangia. In the type species, the zygospore is described to be ovoid to globose, but in strain JOJ, the shape seems to he variable, depending on the size and shape of the conju. gation tube. The spore wall is l-layered, smooth and yellowish.brown in color. SPIROGYRA Link, Bonn. Link, H. F Epistola de algis aquaticis in genera disponendis. Filaments inbranched, vith cylindric cells; cells 0.5-JO times as long as broad, vith plane, colligate, semireplicate, replicate or unduliseptate septa; chloroplasts 1-16 par cell, spirally arranged,parietal, ribbon-like, vith numerous pyrenoids; nucleus centrally located, held by p:totoplasmic strands.

61 35 Reproduction by, ald.net8s, aplanospores, zygospores oi parthenospores; conjugation 8calariform or lat&ral; zygospores ellipsoidal, or ovoid or lenticular; apàtanwa1ll3-5 layered, median wall pale yellow to chestnut brown in color and smooth or variously ornamented. spmooira JUERGERSII Kuetzing, (fig. 4,-49) Kuetzing, Phycologia Germanica, p Transeau, The Zygnemataceae, p. 151, Pl. l fig. 1 & Pl. IXI, fig. 3. Randhawq p , fig Gauth1er-L1~vre, p , Pl. XXXIX, fig. e. & Pl. XL, fig. b-c. Vegetative cells Jl wide and P long, with plane occasionally swollen end wall; one chloroplast per cell, making 2-7 turns. Reproduction by akinet&s, aplanospores, and zygospores; akinetes cyl1ndrically inflated, 48-60fiwide and p.long with thick wall; conjugation scalariform and lateral; tubes formed by both gametangia; fertile cells cyl1ndric or enlarged towards the middle (to J4 }1); zygospores and aplanospores ellipsoid to cyl1ndr1c-ellipsoid, p wide and p long; spore wall 3-layered.; Median wall, yellow and smooth. GEOGRAPHICAL DISTRIBUTION U.S.A.; South America, Australia (Transeau 1951); Afnca (Gauthier Li~vre, 1965); India (Randhawa, 1959). STRAINS: 211, and 215. The vegetative cells of strains 211 and 215 are longer than the type, being upto 200 fol long. The end walls are plane and usually swollen in the reproductive cells. Strains 211 and 215 go sexual readily in soil ~ter bottles and on agar plates. In soil water bottles they form zygotes 6-8 weeks after subculturing. On Agar plates a 3-5 week old culture goes sexual in 3-4 days. The process of conjugation is initiated hw the formation of conjugation tubesby both the gametangia. The portion of the tube formed by the male gametangium is consistently longer than the one formed. by the female. The male gametangia are generally smaller in length than the female, and are cyl1ndric and not swollen. Whereas the female gametangium is sl1ght4r awollen in the middle. The sterile cella, especially of the male filaments are seen to form

62 Spirogyra juergensii Kuetzing Fig. 45. A végetative eeil. X 210 Fig. 46. Early stage in scalarif'orm. conjugation. Note the unequal length of' male and f'emale gametangia. X 180. Fig. 47. Migration of' the male gamete. X 180 Fig. 48. Plasmog~. X 180. Fig. 49. Late stage in scalarif'orm. conjugation. X 250.

63

64 ,fj;4,"-:.. ~"'. '.,,. ~t.i"î~_;;,.... ~. ".. ~, ~,- ' -./.~:.,.. ~.:,'. - -' /.f\.'. ~ 1 i i 1 / ; j 48 49

65 37 papillae-like outgrowth, which look ver,y much like the conjugation tube. Even the protoplast in these cells is seen to contract but thick-walled spores vere never observed.. The protoplast of the male gametangium contracts before that of the female and migrates into the female gametangium. Plasmogamy occurs and zygote is formed in the female gametangium. Zygospores are ellipsoictl to cylindric-ellipsoid, vith 3 wall layers. The outer and inner thin, smooth and hyaline, and the middle more or less thick, smooth and,yyellowish. SPIROOIRA GRACILIS (Hassall) Kuetzing (fig ) Kuetzing Species Algarum, p Transeau, The Zygnemataceae. p. 152, Pl. XXI, fig. 5. Randhawa, The Zygnemaceae. p. 296, fig Gauthier-Li~vre, Zygn_cées Africaines, p. 122, Pl. XXXVIII, fig. b-d. Vegetative cells 16-24)!- vide and )l long, vith plane end walls; chloroplast one par cell making t to 6 turns. Conjugation scalariform; conjugation tube formed by both gametangia;!emale gametangia swollen, mostly on the conjugating side; zygsopores ellipsoid vith rounded ends, Jl vide and 4O-65)l long; spore wall 3-layered, Median wall smooth, yellow-brown. GEOORAPHICAL DISTRIBUTION Europe, China, Siam, U.S.A. (Transeau, 1951); India (Randhawa, 1959); Algeria, Tunisia, am Morocco (GAuthier-Li~vre, 1965). STRAIN: 203. Strain 203 goes sexual readily both in soil-water bottles as weil as on agar plates. In soil-water bottles, it goes sexual 6-8 weeks after subculturing, whereas, on agar pute, a 3-4 week old culture forms zygotes in 3-4 days. On agar plates it also forms rhizoids at places, more frequently at the tips of the filaments. Those rhizoids are typically unicellular, narrow and usually unbranched (rarely branched). Occasionally, more than one rhizoids

66 38 Spirogrra graoilis (Hassall) Kuetzing Fig. 50. A vegetative cell. X 45. Fig. 51. Early stage in soalaritorm. conjugation. Note both gametangia are oylirdrio and not swollen. X 100. Fig. 52. Soalaritorm oonjugation. Note the swelling ot temale gametangia. X 100. Fig. 53. Migration ot the male gamete. Fig. 54. One female filament oonjugating vith two male filaments. X 45. Fig. 55. An aplanospore. X 240.

67

68 (,... 't 55

69 39 are.,formed by one celle The ceus giving rise to these rh1zoids are irregularly swollen. At the onset of the conjugation process, two complementar.y filaments lie close to each other. Conjugation tubes are formed by the ceus of both ~~ filaments of' a pair. At this stage, the cells of the two filaments are almost identical and i ts impossible to say which is going to be male and which one f'emale. It is interesting to note at this stage, that the conjugation tube is f'ormed by both gametangia, although at later stages, it appears to be formed by the male onlj. Subsequently, diff'erentiation of the wo gametangia occurs. The male gametar.gia look very much like a vegetative cell, except for the large amount of' the reserved photosynthate. But the f'emale gamet&ngia swell considerably, more towards the conjugating side. The contraction of the protoplast starts in both the gametangia even bef'ora the wall between the conjugation tube is dissolved, and is f'aster in the male than in the f'emale. The contarcted protoplast of the male gametangium or the male gamete has an irregular shape. The male gamete m1grates into the f'emale gametangium soon af'ter the wall between the conjugation tube is dissolved. Plasmogamy occurs and the zygote is formed in the female gametangium. The zygospore is ellipsoid with threelayered smooth wall. The outer and inner layers being hyaline and thin. and the middle thick and yellowish-brown. Aplanospores resemble the zygospores in structure of the wall and shape. The aplanosporangia are swollen. SPIROGYRA REFLEXA Transeau Transeau, Ohio J. Sei. 16: 28. and The Zygnemat&ceae. Ohio State University, Columbus. p. 200, Pl. XXXIV, fig Randhawa, M.S The Zygnemaceae. Indian Council of Agri. Res. New Delhi. pp , fig Vegetative cells p wide and p long, with plane end walls; one chloroplast par ceu (rarely two), making 3-12 turns.

70 40 Spirogyra :-eflexa Transeau Fig. 56. A vegetative cell$ X 200 Fig. 57. Early stage in conjugation. Note geniculation. X 100 Fig. 58. Late stage in conjugation. Note the migration of gamete. X 100 Fig. 59. A zygospore. X 250

71 _.,. ;. TA

72 c... '1 ", '/ 56 i 58 (.. :.... :. - '-',

73 41 Filaments geniculate; conjugation scalariform; tubes formed by the male gametangia onl.y; female gametangia swollen on both sides and strongly renexed, single or in groups of 2 or 4; zygospores, parthenospores and aplanospores ellipsoid, p. vide and )l long; zygsopsore vi th 3-layered wall, outer and inner smooth, thin and hyaline and the middle thick, smooth and 18llvwish-brown. GEOORAPHlCAL DISTRIBUTION U.S.A. (Transeau, 1951); Bihar, India. STRAIN: 206 Strain 206 has smaller measurements than the type species. The vegetative cells of strain 206 SIm }l vide as compared to 30-44)l. of type species. Similarly, the zygospores of the strain 206 are smaller than the type, being on-ly )l wide and 34-64)l long as compared to X Jl of the type species. In other resp.ects, the two are strikingly similar. the filaments of strain 206 geniculate regularly, 4-5 weeks after subculturing in the soil water bottles and form net-l1ke masses, but were never observed to proceed any further towards scalariform conjugation. On the other hand, if some of these geniculating filaments are transferred to agar plates, the scalariform conjugation occurs and zygotes are formed in 3-4 days. Similarly, if rapidly dividing (i.e. non-geniculating) filaments from a 2-3 week old culture are transferred to agar plates, they geniculate and then proceed further to complete the process of conjugation. Thùs it appears that the process of geniculation, like in certain apecies of Mougeotia.~.i!1. angolensis and!1. acalaris) examined in this study, is a necessary prerequisite to acalariform conjugation in this strain. The male gametangium forma the conjugation tube. The female gametangium swells on both sides and

74 42 becomes fusiform in shape. The protoplasts of both the gametangia contract. considerably. Then the male gamete migrates into the female gametangium. Zygospores are ellipsoid, cval or irregularly shapeti, single or in smau groups of 2-4 and not in long chains. Occasionally, the gametes fail to ruse and form parthenospores in both gametangia. The parthenospores are usually s1m1lar to zygospores in shape am wall structure. SPIROGYRA CONDENSATA (Vaucher) Kuetzing (fig ) Kuetzing, Phycologia Generalis. p Kolkwitz & Krieger, Zygnemales, In; Rabenhorst's Kryptogamenflora von Deutshcland und der Schweiz. 13, Abt. II. p. 318; fig Transeau, The Zygnemataceae. p. 152; Pl. XXI, fig. 11. Randhawa, The Zygnemaceae. p : fig Gauthier-Li~vre, Zygnémacées Africaines. p Vegetative cella 38-65)l vide and Jl long, vith plane end. walls; one (rarely two) chloroplast per ceu, amking 1-14 turns. Conjugation lateral and scalariform; in lateral conjugation zygospores usually in pairs: in scalariform conjugat1on both gametangia for the tubes; both male and female gamet&ngia, cylindric and not swollen; zygospores oval to euipsoid 32-45)l broad and 48-10)l long vith 3 layered wau; the Middle wall smooth and brown in oolor.ïzygospores in forms reproducing by means of scalariform oonjugation are larger, being ~ broad, and p long; sterile oells vith thickened mucilaginous walls, frequently alternate vith the male cells. Parthenospores common, rounded, 24-26)l in diameter or similar to zygospores in shape and. size. GEOGRAPHlCAL DISTRIBUTION U.S.A.; Europe; South Amerioa (Transeau, 1951), India (Randhawa, 1938) and Afrioa (Gauthier-Li~vre, 1965). STRAIN: 202. The vegetative cells of the strain 202 are usually much longer than the one described before (Randhawa, 1959), baing u~o 5 times as long as broad. The chloroplast 1s also observed to be more tvisted, 2-14 turns. It is interesting to note that Randhawa (1959, p. 292, line 2) has mentioned

75 43 Spirogyra condensata (VAucher) Kuetzing Fig. 60. A vegetative celle X 125 Fig. 61. Lata stage in lataral conjugation. X 175 Fig. 62. Late stage in scalariform conjugation. x 125 Fig. 63. Early stage in scalariform conjugation. Note that two male gametangia have made contact wi th one female gametangium. X 125 Fig. 64. An aplanospore. X 175

76

77 ;;-:-~ 1; ) /. / -'- il,'./ ; \ f- I l 63 64

78 44, '44 the chloroplast m.ald.ng only 1 to 2i turns, although the drawing on the same page (fig. 245, a). shows 6 to 8 turns. strain 202 undergoes sexual reproduction both in soil water bottle as well as on agar plate. In soil-water bottles, zygospores are formed in 6-8 weeks after subculturing, whereas on agar plates a 3-4 week old culture forma zygotes in 2-3 days. In the liquid medium, the most frequent method of conjugation is lateral; scalariform conjugation being rare. On agar plates, both the lateral as well as scalariform conjugations are quite common, although Most of the zygotes are formed by lateral conjugation, whereas zygotes are infrequently formed by scalariform conjugation. The same filament is observed to undergo both lateral as well as scalaritorm conjugation. The conjugation tube is formed by both gametangia. The protoplast of both the male and female gametangia contract considerably bafore the malegamete migrates into the female gametangium. The zygotes are formed in the female gametangia and are variuusly placed, i.e., the long axis of the zygote May ba parallel, oblique or at right angles to the length of the filaments. Parthenospores are common in the filaments undergoing both lateral as well as scalariform conjugation" and are identical to zygospores in shape, size and wall structure. Usually the parthenospores are formed in the female gametangium. SPIROOYRA LIANA Transeau Transeau, Trans. Amer. Microscop. Soc. 53= 228; Pl. XXI, fig. 56. / and The Zygnemataceae. p. p ; Pl. XXXIII, fig Randhawa, The Zygnemaceae. p Vegetative cells p vide and p long, vith plane end walls; one chloroplast per cell, making 2-7 turns. Conjugation scalariform and lateral; conjugation tube formed by male gametangium; female gametangium swollen on both sides, single, paired or in

79 45 Spirowa liana Transeau Fig. 65. A vegetative celle Fig. 66. Ear~stage in scalariform conjugation. Note that conjugation tube i8 formed by both gametangia, and both gametangia are cylindric at this stage. X 120 fig. 67. Early stage in scalariform conjugation. Note that the female gametangium has swollen. X 120 Fig. 68. Lata stage in conjugation. X 120

80

81 65., '1 ;1 1 " i. r ' ",1 1./,. 67 l '.,. '

82 46 short chains; zygospores ollipsoid, JI wide and 35-52}1 long, spore wall 3-layered, median wall yellow, smooth. GEOORAPHICAL DISTRIBUTION STRAIN: 209. Szech~an and Kiangsi, China; Sweden (Transeau, 1951); Bihar, India. Based on cell dimensions, strain 209 appears to he intermediate between.. liana and., chenii. The two species differ primarily in the vidth of the vegetative cells,.. liana being ~ vide and 2. chenii p, whereas, the width of the vegetative cells of the strain 209 is )1. With respeot to other morphological features, these two species are also similar except for tbeshape of the female gamet&ngia. In.. liana, only the central part of the female gametangium is swollen ( Randhawa, 1959; p. 349; fig. 357), whereas, in S. chenii, it is swollen throughout the length, maximum in the Middle and gradually tapering on both sides (Randhawa, 1959; p. 379: fig. 420). Based primarily on this character, the author preferred to regard strain 209 as.. tiana. The strain undergoes sexual reproduction readily both in soil-water bottles as well as on agar plates. In the bottle, the zygospores are formed 6-8 weeks after subculturing. On agar, a 3-4 week old culture forms zygotes in 3-4 days. Unlike the type species, strain 209 reproduces by scalariborm conjugation only. The process of conjugation is initiated by the formation of conjugation tube. At this early stage, the two gametangia look alike andd. have the sarne width. The conjugation tube i8 formed mainly by the male gametangium, the female gametangium only forma a short projection. But the female gametangium starts swelling on both sides soon after the tube is formed. The swelling is very characteristic, it includes only the Middle portion of the

83 gametangium. The width of the remale gametangium near each end remains unchanged. 47 This is more evident in the longer gametangia. The drawings of~. liana (Randhawa, 1959) shaw this characteristic snlling. On the contrary, in,. chenii (Randhawa, 1959) the female gametangium snlls throughout its length. The lj8.1e gametangium does not change its shape. After the snlling of the female gametangium is complete, the wall betnen the conjugation tube and the female gametangium dissolves. The protoplast of the male gametangium starts to contra ct and ndgrate into the female gametangium. At this time, the protopiast of the female gametangium also starts contracting. The process or contraction is very slow in both gametangia. Plasmogamy occurs and the zygote is rormed in the swollen portion of the female gametangium. The zygote, first secretes a thin wall arounc! itself. The mature zygospore has.3-layered wall, the ndddle of which is yellowish-brown in color. SPIROGYRA PRATENSIS Transeau (fig ) Transea~1914. Amer. J. Bot. 1: 292. and The Zygnemataceae. p. 159; Pl. I, fig. 7 & Pl. XXII, fig Randhawa, The Zygnemaceae. p ; fig Gauthier-Li~vre, Zygnémacées Africaines. p ; Pl. L, fig. D d-d'. Vegetative cells )l wide and }l long, with plane end walls; one (rarely two) chloroplast per ce11, making 1-9 turns. Conjugation scalariform and lateral; conjugation tubes formed by both gametangia; female gametangia swollen on both sides, inflated to.38p; sterile cells cyl1ndric or swollen to 90~ in diameter; zygospores, and aplanospores in most cells ellipsoid, in others ovoid to cylindric-ovoid, 24-,36 )l wlde and ~ long; spore walls.3-layered, outer and inner layers smooth, hyaline, mediuan layer smooth and yellowish in color. GEOGRAPHICAL DISTRIBUTION Pe~ping, Nanking (China); U.S.A. (transeau, 1951); Africa (Gauthier Li~vre, 1965); Bihar, India. STRAINS: 210, 21.3, 221, ~ 222.

84 48 Spirogyra pratensis Transeau Fig. 69. A vegetative celle X 75 Fig. 70. EarlY stage in scalariform conjugation. Note female gametangia are cylindric. X 45 Fig. 71. Early stage in conjugation. Note the swollen femalè~ gametangia. X 75 Fig. 72. Late stage in scalariform conjugation. Note the migration of the male gamete. X 75 Fig. 7~. Late stage in scalariform conjugation. X 210 Fig. 74. Single female filament with two male filaments. X 45

85 72 74

86 ( ( (

87 49 The strains undergo sexual reproduction both in soi1 water bottle and on agar plates. In soil water bottles, zygotes are formed 7-9 weeks after subcultur1ng, whereas on agar a 3-4 week old culture goes sexual in 3-4 days. Unlike the type, strains reproduce only scalar1form conjugation. Aplanospores were not seen e1ther, although parthenospores were not uncommon. The process of conjugat1on 1s initiated by the formation of short papillae on both of the complementary filaments. TheBe filaments, at this stage, look exactly identical and it is difficult to distinguish the male and the female gametangia. Soon, the papillae of the complementary gametangia meè.t,'!;o forn.the conjugation tube and the cells destined to form female gametangia undergo further differentiation. These cells swell throughout their length, being widest in the Middle and gradually tapering on both ends.,the male gametangia usually do not swell and have the same diameter as the vegetative cells. Ocass~onallY, some of the male gametangia do show slight swelling in the region of the conjugation tube. The protoplast of both the male and the female gametangia are filled with starch. Generally, when conjugation was observed in these strains, a most interesting sexual phenomenon occured. Single female filaments were found lying between two male filaments and the female gametangia formed conjugation tubes with two and rarely with more of the male gametangia. These filaments were observed until the conjugation was complete and o~ one male gamete was found to be functional and underwent plasmogamy with the female gamete. The contents of the female gametangia start contracting first, even before the -., _~.:.-.' " >~, ;':.~'l'_~ wall between the two conjugation tubes has dissolved. After the wall is dissolved, the male gamete migrates into the female gametangium, plasmog~ occurs and the zygote is formed. The zygotes are generally, ellipsoid in shape, Jl wide and 45-72)l long,with 3-layered wall, Middle of which is yellow and smooth. The conjugating filaments do not undergo ~ marked geniculation as

88 50 a result, the zygospores are usually formed in chains. But swollen sterile cells on both female and male filaments are not uncommon. SPIROGYRA HYALlNA Cleve (fig ) Cleve, Nova Acta Reg. Soc. Sei. Upsali Er. J. 6: 17; Pl. J, fig Transeau, The Zygnemataceae. p. 170; Pl. XXVI, fig Randhawa, The Zygnemaceae. p. J18; fig Gauthier-Li~vre, Zygnémacées AfriGaiü6s.. p Vegetative cells 45-60~wide and u long, plane end walls; chloroplasts 2, J, or 4 per cell, amking i to 4 turns. Conjugation scalariform or lateral; tubes formed by both gametangia: fertile cellà (both male and female) cylindric or slightly swollen: zygospore ellipsoid, more or less pointed, )l wide and }l long: spore wall J-layered, mè.dian wall brown, smooth and thick, outer and inner walls hyaline, smooth and thin: parthenospores.similar to zygospore, somewhat smaller. GEOGRAPHlCAL DISTRIBUTION: 1959). China, Sweden, Puerto Rico, U.S.A. (Transeau, 1951): India (Transeau, STRAIN: 208. Strain 208 goes sexual readily both in soil-water bottles and on agar plates. In soil-water bottles, it usually, forms zygospores 8-10 weeks after subculturing. On agar plates, li. J-5 week old culture forms zygotes in J-4 days. It reproduces only by scalariform conjugation and parthenospores. The conjugating filame~ts do not undergo ~ geniculation, as aresult, the zygospores are formed in chains. The sexual p~ocess is initiated by the formation of conjugation tubes between the pairs of gametangia. The gametangia, both male and female, show little or no swelling (on the conjugating side). The male gamete migrates into the female gametangium soon after the wall between the ft conjugation tube is dissolved. Plasmogamy occurs and the zygote is formed...,in the female gametangium. Occasionally, the male gamete does not migrate

89 51 Spirowa hyalins Cleve Fig. 75. A vegetative cell. X 120 Fig. 76. Lata stage in scalaritorm conjugation. X 120 Fig. 77. Parthenospores in both male an! temale gametangia X 120

90 15. '...':-~j. ~-_.,', Il''' '-...' :.!I~, ~\~\:...,,;,.... {.", \p.' ~ 1." M " _.'2'.'. ~~ ".-:".,'76 :

91 C) 1 i J,'1 1.1,,. -1., 1 1 :.! (), 1

92 5 2 into the lamale gametangium even though the wall in the conjugation tube is dissolved. In such cases, parthenospores are lormed in both the male and lamale gametangia. These spores are smaller than the zygospores. The zygospores and parthenospores are usually ellipsoidal in shape and lirst lorm a thin wall around themselves, two more layers are laid down later. The outer and inner layers are thin, hylaine and smooth and the Middle layer is yellowish-brown, thick and smooth. SPIROGYRA IRREGULARIS Naegeli (fig ) Naegeli,1849. In: Kuetzing's Species Algarum, p Kuetzing, Tab. Phycol. 5: Pl. 23, fig. 2. Transeau, The Zygnemataceae. p. 168 Pl. XXVI, lig. 4. Randhawa, The Zygnemaceae. p. 316, lig Vegetative ceus p. wide and )J. long, with plane end walls; chloroplast 2-4 (usually~) par cell, making t to 4 turns. Conjugation scalarilorm; tubes lormed by both gametangia; fertile cells cylindric; zygospores ellipsoid to cylindric-ellipsoid, p wide and ~ long; spore wall 3-layered, Middle of which yellowish-brown, smooth. GEOGRAPHlCAL DISTRIBUTION STRAIN: 207. Western and Central EuropeJ U.S.A. (Transeau, 1951); India. The cells of strain 207 have plane end walls, but when the cells separate, at the end ol one of the two separating cells, a ring of ceu wall mate rial is seen attached, which looks like H-pieces of 2. colligata (Hodgetts, 1920) and of 2,. nitida &ffinis (Gibbs, 1926). On careful examination, it was observed that the outer layer of cell wall does not break right outside the plane of the transeverse wall, but a little towards one of the two ceus. This results in a ring of cell wau material ~ttached to one broken end whilst the other lacks it. Strain 207 goes sexual both in soil-water bottle and on agar plates. In soil-water bottles, the process is very slow. Signs of conjugation are

93 53 Spirogvra irregularis Naege1i Fig. 78. A vegetative oe11. X 120 Fig. 79. Ear~ stage in soa1ariform oonjugation. Note the intaot male filament with separate female oe1ls. X 120 Fig. 80. Soa1ariform oonjugation. Note the migration of gamete. X 120 Fig. 81. Ear1y stage in soa1ariform oonjugation. Note septum between two female garnetania has disso1ved. X 60 Fig. 82. Late stage. Note the tetraploid zygospore formed by the fusion of two diploid zygotes. X 60

94 81 82