~ eh States esey et SAS Meg SAAN =| =) 2) = Q ea Q Z < > < am | MAMAN 0 wi MBL/ MM WW George M. Grav i Mari . Museum ee wological ie f: Bloods Hole, Mass raboratory 6 S4 THE ZY GNEMATACEAE Fonte ’ ) Py) oe ya . WAR aise aie ert aC ar re i ze - rey j Hy } THE ZYGNEMATACEAE (FRESH-WATER CONJUGATE ALGAE) With Keys for the Identification of Genera and Species and Seven Hundred Eighty-Nine Illustrations By Epcar NeLson TRANSEAU Emeritus Professor of Botany The Ohio State University THE OHIO STATE UNIVERSITY PRESS Columbus 1951 GRADUATE SCHOOL MONOGRAPHS CoNTRIBUTIONS IN Botany, No. 1 Copyright 1951 The Ohio State University Columbus Printed in United States of America )03b To the Graduate Students who discovered many new species and extended the known range of many other Zygnemataceae ‘ f| yg" Ke) } : INTRODUCTION The absence of a modern general key with detailed descrip- tions of the species belonging to the Zygnemataceae has greatly retarded the study of this family. This volume, it is hoped, will furnish a better manual for the identification of the genera and species than has been previously available. It seems self-evident that any studies of life histories, seasonal and cyclic abundance, and geographic distribution must be based on the accurate naming of the species considered. In addition to the literature about the Zygnemataceae, the present descriptions are based on data and specimens accumulated over a period of thirty-five years. My interest in the group was originally stimulated by Mr. Frank S. Collins, who sent me many specimens he had collected, or received by exchange. These specimens were soon augmented by exsiccatae from Professors Borge, Nordstedt, Farlow, and Thaxter. These included numerous type specimens from many sources, and made possible the revision of earlier descriptions and the devising of new keys for the separation of species. Mean- while, thousands of collections became available for study through the collecting activities of associates, graduate students, and myself throughout the eastern half of the United States, and from Ontario to Cape Breton Island. From Finland, Latvia, South Africa, Central and South America, Puerto Rico, China, India, Japan, and the Philippine Islands, several hundred additional col- lections have been received from correspondents. During the most active period of the study of these collections, I had the assistance of Professors L. H. Tiffany and C. E. Taft, who checked literally scores of the determinations and verified numerous de- scriptions of new species. To them I am most grateful for their help, and for the feeling of satisfaction that the new descriptions, particularly of spore walls, have been verified by at least one other pair of eyes. Whether one accepts all of the genera, or all of the species, as valid or not, they seemed to differ in enough particulars to war- rant their separation at the time they were studied. Some of the species described during the early history of the group have been vu Vii ZYGNEMATACEAE omitted because of faulty descriptions. Also some recent descrip- tions have had to be passed over because they lacked important details, or because of discrepancies between figures and descrip- tions. I have no doubt that some of these species are valid, and if additional information could have been obtained, they would have been included. No attempt has been made to guess at the synonomy of all previously published species names. Such guesses can be found in the Sylloge Algarum by G. B. de Toni (1889), in the Siisswasserflora Mitteleuropa, 9 (1932), and in Rabenhorst’s Kryptogamenflora, 13 (1941-44), abt. II. In the absence of complete descriptions, or of the actual specimens, such conjectures seem gratuitous. Synonyms that are the result of different con- cepts of generic or specific limits are usually given. A few species with incomplete descriptions, but with conspicuous structures that distinguish them from other somewhat similar species, have been retained. Among the many friends and students who have contributed collections containing Zygnemataceae, I am particularly indebted to Alma Ackley, Wayne University; Charles C. Adams, New York State Museum; D. B. Anderson, Agricultural and Technical College of North Carolina; the late W. M. Barrows, The Ohio State University; Glenn W. Blaydes, The Ohio State University; E. T. Bodenberg, Wittenberg College; Harold C. Bold, Vander- bilt University; Helen B. Bromley, Stamford, Connecticut; Charles Bullard, late of Harvard University; C. Cedercreutz, Helsingfors, Finland; Glenn Couch, University of Oklahoma; Francis Drouet, Chicago Natural History Museum; R. B. Gordon, Westchester Teachers College; Lawrence Hicks, Columbus, Ohio; Elwyn Hughes, University of Oklahoma; G. J. Ikenberry, Oklahoma Agricultural and Mechanical College; Chin-Chih Jao, Chungking, China; Minnie M. Johnson, Stephens College; Ivey Lewis, University of Virginia; Liang Ching Li, Fan Memorial Institute of Peiping, China; Floyd A. McClure, Lingnan Uni- versity; B. B. McInteer, University of Kentucky; George Nichols, late of Yale University; Claude E. O’Neal, Ohio Wesleyan Uni- versity; Gerald Prescott, Michigan State College; M. S. Rand- hawa, Fyzabad, India; H. C. Sampson, The Ohio State University ; H. Skuja, Uppsala University, Sweden; Ben H. Smith, Indiana State Teachers College; G. M. Smith, Stanford University; Edith L. Stephens, University of South Africa; E. L. Stover, Eastern INTRODUCTION 1X Illinois State Teachers College; Clarence E. Taft, The Ohio State University; Hiram Thut, Eastern Illinois State Teachers Col- lege; L. H. Tiffany, Northwestern University; and Larry Whit- ford, Agricultural and Technical College of North Carolina. In checking the descriptions, keys, and references, I had the assistance of Mrs. Maynard Hale and Mrs. Robert Sigafoos. They added much to the accuracy of the text, the indexing, and the uniformity of the references. Professor John L. Blum of Canisius College, Buffalo, copied or adapted many of the published figures and added many new figures and details of spore walls. Without his help the publication would have been greatly delayed. I am grateful to each of these associates for their contributions to the usableness of the keys. The Graduate School of The Ohio State University has aided in the editorial work, and in the preparation of the figures and plates. It is a pleasure to acknowledge this financial assistance. No attempt has been made to draw the figures to a certain scale of magnification. Since the descriptions give the dimensions, the principal value of the illustrations is the form of the various structures associated with reproduction and the details of spore- wall markings. The 789 figures illustrate 534 species, and all of the known types of gametangia and spores. ESN. Co_umesus, Ou10 1950 ‘ 7 aH : ee a ; y i ; \ . wey : j | A! ret Wh 7 a * F TA) i , sha ra © bee we j i ! oil ‘ \ : 4 \ ot Abas i 4 sy i e ' ys ay ' =) @ f is tks Ari al “ J 4 tm ‘ ' rf wes ws. . ben) 2) 1 rust? he ae iy Mie tid Hada > Sa coc. ; Bert) | Owes, tone, gee . ba bie -YY Mp LAG ty hat cae tn j _ ay: > ‘ 7 we : ee a Pr ae Paak tek Fy ost x y c. i. iw, vith, v ; Veen’ mt er bs | 1 aga t aul ‘ia , Ce tae . hi fic extent, etsea Gn a eee : 1 ‘ Jat j ein i+ i rae . , is ‘a Fi Un ; , yi ae he ee a 7 fl i. j :“) ji ibe Ce iP " ry ; been OO PA ; wisi y ’ ee i Sve Ron —r om Pe iv pola ery, ah Oe ade? We ‘" As eer ee TREE LA a ie Paget ety fae My Bh a iis ay eae ny iy i io - ape he Ne ri AC ty ae ina an na si es ae be ar mi < ty : cine mi) ie Y | a a oe a ; aaa si Pay tit Be ieee . Y Chapter Es i: CONTENTS General Taxonomic Characteristics—The Order Zygnematales if GEN Srnithy iOS ae terse aicr theeaicle i lela at auayespeptanees area she sou 3 The Genus Zyonema, CA. Agardiy 18247. sc nesses oe © 13 The Genus Zygnemopsis (Skuja) Transeau 1934............ 49 Whe, Genus Fallasa Rosenvinee, 19245 . 3. jes 2 ot) om ainsi 61 The Genus Zygogonium Kitzing 1843.........+......2000- 63 ane Genus Pleurodiscus Vagerheim 1895 * 5...) -/.)..2.)4 42 71 the Genus iMonceonapas Palla T894.).. chat cise «2 avapate ake 73 hes Genus Wevaryas Witthock 1872. v0 \ betes ess cc maleletereses "5 M@he Genus Mougeoria C. A. Agardh 1824. 00206050. alos ae 79 The Genus Temnogametum W.& G. S. West 1897.......... ey) The Genus Sirocladium Randhawa 1941.......-.0+0eeeee eee 11g The Genus Entransia Elwyn Hughes 1943.............0005: 21 he Genus Spirogyra (om 1820. - ce Qt eouiar aatse meleieds 123 The Genus Sirogonium Kutzing 1843. ......+....05022206%. 231 DAE Veo aN RIL aN aE SST cae Sang RRUNE TC gta ay at pec U aie CIS 3 6 239 ae MC AINA Ml Ao. teH len Sta by ofa Sealtaigp seen ater’ s eakaga eet ePeReeae 247 (ae : s ul. at A ‘ « ’ r er a 7 te wy ; 7 whe + a Me ‘ae a , Ls a : ILLUSTRATIONS PLATEs Page Reproductive Structures of Zygnemataceae............-. 246 EMEP CL ta Nate seve iste es i ods cx cee Se eaw nas o anv nes ee 302 Rs SPIRO RE rehashed vam ienltiy on bx « ones ee ae 304 DON PSNI OY EE To istak arcie aise paren Ov en ac «a a eh ee 306 PIRES | PODS 5 Ae Savi icin lalp ee wha b>: alow Phelan tee eA 308 PRAIA IT, 1 TORY Boos vii: wh inv eid sete wtiv's: dik wi ew ware le bes 310 DON ee SEVODUIIE \ alo c aie «aren she a sii das dso des RN RO en 312 Bh i A POLE 55 sit neh catnip ne ate is @ bea eT Oe lee 314 RWS UII OUII cf ois aalat hin Weiesateta Moye piss tale: ee nee a ee ge 316 ER NA; EIS PRALITE uc sidcd sins laceinhc Said hala lation af bibtoaWea «oleh ara 318 Re LLL FPA QTE i nice aya acot s iw Sontn\s ib antey sb. ae pe ae AT 320 Osh DRT ORUTE ace dail. chins shod eae sak). eee ee 322 Phe SIO ROME ihc alas x odoin we nus wits ace eee eee a 324 XLI. Zygogonium, Zygnema, and Spirogyra ............008 326 ILLUSTRATIONS IN TEXT Figure Page Pf VCE: BM PIOIMCUA FI i ip. aap wie eS Ak si wees 3 44 BS “LV GREINE PUI 8 io BEES Sa stein ss 0 Ave» 803 0 ce 44 Pos UCLA! NGANEE os p= 56> see sash 2 RSet ke soe a 45 Me DOIN IVR. i i5 a 18 dae asa Ss Cab ecke AK aks hes et 193 XS! SOU GOMIN I FHCREED: ois cicin aire n e590 58 iws 68 oa 233 Fi-K SiO poser PAACOEPOPIIR ii sho thin sic vend ono 8 oe EOE 236 THE ZY GNEMATAGEAE } ay cA | M ‘es rape ! os “uit Ne he . ¢ 4 Ne f a ice CHAPTER ONE GENERAL TAXONOMIC CHARACTERISTICS THe Orper ZYGNEMATALES G. M. SmitH 1933 The plants belonging to this order of the Chlorophyta differ from all other green algae in the absence of free swimming flagel- lated gametes and spores; sexual reproduction is consummated by amoeboid gametes through, or within, a tube, pectic sheath, or an enveloping pectic mass. The plants consist of single cells, of loose cell aggregates within a pectic gel, or of unbranched or very sparsely branched, and usually undifferentiated, filaments. The cell walls have an outer pectic layer and an inner cellulose layer. The spore walls consist of at least three layers, the inner and outer of which are of cellu- lose, and the median wall of cellulose with varying amounts of chitinous deposits. The median wall may be colored yellow, brown, or blue. The chromatophores may consist of axial or parietal plates, or spirally arranged parietal ribbonlike structures, or of two axial stellate bodies often highly diversified among the desmids. The zygospores have a dormant period during which there is a fusion of the gametic nuclei followed by a reduction division. At the time of germination the four resulting nuclei may each become the center of a new cell, or two or three of the nuclei may disintegrate and only two or one sporelings emerge from the spore wall. The Zygnematales are naturally divided into three families which have, briefly, the following characteristics: FAMILY I. ZYGNEMATACEAE These are filamentous plants, usually unbranched, and have cylindric cells. The walls of the vegetative cells are unseg- mented and without pores. The chromatophores are either axial more or less stellate, ribbonlike or platelike bodies; or are parietal platelike or spirally arranged ribbonlike bodies. Conjugation of 3 4 ZYGNEMATACEAE gametes is by means of a tube between the gametangia, or some- times by a mere opening between the adherent gametangia. The zygospores are formed either in the tube or within one of the gametangia. FAMILY 2. MESOTAENIACEAE Vegetative cells are solitary, cylindric or spindle-shaped, or sometimes loosely united into filaments within an amorphous pectic gel or pectic sheath, and without wall pores. Chromato- phores are stellate, platelike, or ribbonlike and spirally arranged. Conjugation of gametes occurs through tubes of cellulose, or within a pectic gel. FAMILY 3. DESMIDIACEAE Vegetative cells are solitary, or sometimes are united into simple filaments. Vegetative cells have highly diversified and sometimes bizarre forms, but all have transversely segmented walls and wall pores. In most genera the cells have a median con- striction or isthmus between the two nearly symmetrical halves. There may be one or several chromatophores in each semicell with a nucleus in the isthmus. During cell division, after the nucleus divides, the isthmus elongates and the two semicells are separated by a median wall. On both sides of this wall new semi- cells develop from the isthmus. Conjugation is by gametes that emerge from their respective cell walls and unite within an amor- phous pectic sheath or in a conjugating tube. (For further details see G. W. Prescott, “Desmids,” Botanical Review, 14 [1948], pp: 644-76.) Tue Famity ZYGNEMATACEAE Smit 1933 The species belonging to the Zygnemataceae are probably more numerous, and are more generally distributed over the earth than those of any other family of filamentous green algae. The tangled green masses of algae floating on ponds, ditches, and slow streams anywhere are sure to contain representatives of this group. All the species have cylindric cells during the period of vege- tative growth. During the reproductive period, however, the cell walls of some species grow and change their size and form in a most astonishing manner. In some species the gametangia alone are affected. The receptive gametangia in particular may become distended on all sides, on the conjugating side only, or only on TAXONOMIC CHARACTERISTICS 5 the opposite side. The bulges may be rounded, or cylindric with shoulders at both ends, or spindle-shaped. In any event the resulting forms of the expanding cell walls are remarkably uni- form in a given species. In other species many of the nonrepro- ducing cells enlarge and become distended or even bullate. These changes in cell form are definitely the result of hereditary factors. In some environments one may also find vegetative filaments composed of variously rounded or distorted cells, even with rhi- zoidlike outgrowths, in extreme instances. These collections, in my experience, have always been gathered from ponds with warm water and low oxygen pressure. Since these effects were noted on several of the species present, the causes are probably environ- mental. The following key to the genera is based primarily on the characteristics of the chromatophores, and secondarily on the changes that take place in the reproductive cells during spore formation. In the subsequent keys to the species grouped under each genus stress is laid on the characteristics of the spores. Consequently one must be quite clear about the nature of these several kinds of reproductive structures. The simplest, most universally present, and probably the most primitive type of propagating cell is the akznete (PI. 1, Figs. 1-3). This is usually just a vegetative cell, the walls of which have been thickened by additional layers of cellulose, or cellulose and pectose. These cells survive long periods of drought, high and low tem- peratures, as well as the effects of these factors on the concen- tration of solutes in their immediate environments. Akinetes germinate readily and initiate new filaments. Only one species (Zygnema sterile) has been found to reproduce by this method alone. There are probably many others but they are not so easy to identify as this one, which happens to be the largest species of Zygnema in the Ohio valley. There is a prevalent notion that akinetes are formed when conditions are unfavorable. It has been our experience that they develop both when conditions seem most favorable and when least favorable. In cultures, they appear both at high temperatures and low temperatures. The causes for the initiation of akinetes are best stated as unknown. At high altitudes and latitudes the species of Zygnemataceae 6 ZYGNEMATACEAE are common but are rarely found producing spores. These species cannot be identified because the modern species keys are neces- sarily built around spore characteristics. Akinetes are common in collections from these short-season regions, and by means of them survival and propagation of many species take place. There is no good reason to assume that all these species would produce spores in other environments. It is far more likely that some of these species are wholly vegetative, or akinetic. There are other species in several of the genera that also repro- duce by aplanospores. These are slightly more specialized than akinetes. Their forerunners are vegetative cells, the protoplasts of which have contracted more or less, and in which new walls of cellulose, with or without chitinous deposits, have developed. The spore walls may be colorless and smooth, or variously colored, sculptured, and ornamented. The criteria used to distinguish aplanospores in Zygnematales are precisely the same as those used to designate aplanospores among the Ulotrichales (Pl. I, Figs. 4-7). Of the species here described, thirty-seven reproduce regularly by aplanospores, and zygospores have been found in the same filaments only rarely. Scattered aplanospores also occur along with zygospores in seventy-six additional species which belong to 7 genera. Moreover, only a few algologists have been interested in looking for aplanospores or the list probably would be larger. When found, aplanospores have often been written off as algal errors, since most authors state definitely that none of the species of Zygnemataceae “forms asexual reproductive bodies” (Smith 1933), or suspect that they are the result of lateral conjugation (Czurda 1932). The “lateral conjugation” theory rests on state- ments by Petit (1880), W. & G. S. West (1902), with a figure of a disintegrating chromatophore, and figures by Czurda (1931), without nuclei and also with disintegrating chromatophores. The latter series of figures seems to prove only that this unnamed species of Mougeotia may have under experimental conditions lateral conjugation, as have 6 other species in nature. It has little or no significance in proving that the numerous aplanospores occurring in nature which have been carefully studied during their entire development are zygospores. Zygospores result from the union of gametes that are more or less similar in appearance, but physiologically different. The maturation and union of gametes always take place within the TAXONOMIC CHARACTERISTICS 7 walls formed by the conjugating tube and the two gametangia. This conjugation apparatus is relatively persistent and the zygo- spore remains in the enclosure for days or weeks after its own walls are mature. Zygospores at first have two nuclei and either one set of chromatophores (Spirogyra) derived from the receptive gametangium, or two sets (Zygnema and Mougeotia) derived from both gametangia, one of which disintegrates later. After the union of the nuclei, reduction division occurs and four nuclei result. Of these, three disintegrate and the remaining one becomes the nucleus of the basal cell of the sporeling on germination. Only when one contemplates the many successive steps in conjugation from the development of papillae and adhesion of the gametangia onward to the maturation of the spore walls and protoplast, does he realize how very complicated are the chemical, physical, and biological processes that are integrated in zygospore development (PI. I, Figs. 3, 8, 9, and 10). Parthenospores may be formed when the normal union of one gamete with another fails to occur either by absence of an opposite gamete, or by sudden changes in environmental conditions. In some collections gametes are numerous; in others, rare. Partheno- spores can usually be distinguished from aplanospores by their position in the gametangial cells and their relation to adjacent zygospores. It is customary to say that “they resemble the zygo- spores of the same species but are smaller.” Akinetes, aplano- spores, zygospores, and parthenospores have all been seen germi- nating by numerous students. New filaments grow from any of these forms. The taxonomy of the Zygnemataceae has been centered on the conjugation apparatus: its development, forms, and zygospores. The evolutionary history of reproduction in the group, however, must have begun with propagation and survival by akinetes. These are frequently seen in other families of the Chlorophyta. The development of aplanospores must have been a next step in evolution. This is not a large step either, since it implies merely the contraction of the protoplast and the growth of a spore wall. This type of spore also occurs in many other families of the Chlorophyta. When aplanosporangia became differentiated chemically and hormones with plus and minus properties were released which brought about local growth of cell walls followed by adhesions 8 ZYGNEMATACEAE between cells, the first step in conjugation had been taken. Adhe- sion without conjugation occurs in several species of Mougeotia. Conjugation is attained when the double wall formed by adhesion is dissolved locally by enzyme action. The two proto- plasts or gametes are then in direct contact and the conjugating apparatus is established. Obviously the primitive akinetic or aplanosporic species lacked the most characteristic feature of present-day Zygnemataceae until the regular union of gametes through openings between adjacent gametangia became the most prevalent mode of reproduction. From this point of view parthenospores are protoplasts which started up the gametic pathway but had their development ter- minated at the level of aplanospores. Since they contain the same factors for wall color and patterns, the walls of parthenospores resemble those of the aplanospores of the same species. Since zygospores also contain these same factors for wall characteristics, one would hardly expect them to have other wall structures. One would anticipate larger sizes and other forms, since they are the product of two protoplasts. From this point of view, one should say that the walls of zygospores resemble those of the aplanospores rather than the reverse. These surmises concerning the order of development of the several reproductive structures seem far more plausible than the traditional statements and implications that the ancestral form of reproduction was by zygospores, and that the parthenospores and aplanospores have eventuated from the con- jugation apparatus by the loss of factors, enzymes, and hormones. Of the 534 species of Zygnemataceae here described 1 repro- duces only by akinetes, 38 by aplanospores, 494 by zygospores, and 1 has been found only in a vegetative condition. Of the 494 zygosporic species, scalariform conjugation occurs in 400 species; 72 species have both lateral and scalariform conjugation; and 22 species usually conjugate only laterally. Probably all the species propagate by akinetes, and 77 of the zygosporic species also repro- duce by aplanospores. Most spores are colorless, yellow, or brown. Blue spore walls have been found only in the genera: Zygnema (30 species), Zynemopsis (1 species), Zygogonium (2 species), and Mougeotia (8 species). In this family only the zygospores may be hybrid in character following conjugation between different species. The filaments that develop from hybrid zygospores are haploid, meiotic, or TAXONOMIC CHARACTERISTICS 9 gametic segregates. In the few instances in which such progeny have been studied, individual filaments inherit the factor for cell diameters, forms of receptive gametangia, zygospore size, form, and wall markings independently. They are expressed through the cytoplasm of the female gametes. So long as these segregates reproduce by cell division, by akinetes, by aplanospores, and by conjugation between cells of the same haploid filament, the gene complex of the progeny is identical and the filaments are uniform. Doubtless many of the “species” that are collected and named are taxonomic units, or clones, that have originated in this way. Other species seem to have originated by polyploidy and by mutation, but the evidence for this statement is purely circumstantial. The bases for the separation of the genera are shown in the following key. Three genera (Hallasia, Pleurodiscus, and Entransia) are tentatively and purposely defined to emphasize the need for further study of the development and reproduction of these species. All the forms described in this key are designated as “species.” Many variations have been seen in the collections studied but until more is known about hybrid segregates, isolated clones, and the effects of the various environmental factors, it seems unprofitable to assign “variety” and “form” names to every variant. Many alleged “varieties” are not even closely related to the species to which they have been assigned. Key To THE GENERA OF ZYGNEMATACEAE I. Vegetative cells usually with 2 axile chromatophores, which are round, radially branched, pillow-shaped, or disclike, with nucleus contained in the cytoplasmic bridge between them 1. Chromatophores usually a pair of axile stellate or globose radi- ally symmetric bodies, each with a central pyrenoid a) Zygospores compressed-globose or ovoid in the tubes or in one of the gametangia; aplanospores cylindric-ovoid occupy- ing all or most of the cell; gametangia not filled with a dense refractive colloid after conjugation, and without cyto- PlsSMNG FESMMIES). 6.4.26. nse 1. Zygnema b) Zygospores quadrangular-ovoid, or round _pillow-shaped, formed in the extremely wide but shallow conjugating tubes; aplanospores ellipsoid or asymmetrically ovoid; successive layers of cellulose and pectic colloids added inside the gam- etangial walls during conjugation; similar changes occur in 10 i. Ill. IV. ZYGNEMATACEAE sporiferous cells during aplanospore formation; no cytoplas- MG TOMAUES 5.65 RE 2. Zygnemopsts c) Zygospores unknown; 2-7 chromatophores in the cells; aplanospores ellipsoid, on germination 1-3 sporelings develop ERY - PACD acids > 2s sean adele ek 3. Hallasia . Chromatophores a pair of ovoid bodies with, or without, irreg- ular processes, each containing a pyrenoid; zygospores in spo- rangia of 2 cuplike parts with a suture between; aplanospores and akinetes the usual method of reproduction; gametangia and aplanosporangia contain cytoplasmic residues after conjugation and’ spore formation... ....,...'..- 4. Zygogonium . Chromatophores a pair of disc-shaped bodies each with a central pyrenoid; sporangium wall of 2 cups with an equatorial belt between them, otherwise similar to Zygogonium 5. Pleurodiscus Vegetative cells, with single axile, platelike chromatophores with- out pyrenoids; nucleus attached laterally near middle of the cell 6. Mougeotiopsis tv 1eS) Vegetative cells with 1, rarely 2, axile, flat ribbonlike or platelike chromatophores, with several or many pyrenoids; nucleus attached laterally or between the chromatophores when 2 are present 1. Gametangia similar to the vegetative cells before the beginning of conjugation a) During conjugation successive layers of pectic and cellulose colloids are added to the inside of the gametangial walls, filling the lumen; walls of sporangia similarly modified dur- ing spore formation............ 7. Debarya 6) During conjugation as the gametes contract and move to- ward the conjugating tubes granular cytoplasmic residues are left in the gametangia...... 8. Mougeotia 2. Gametangia are short specialized cells cut off near the ends of long vepetative cells... visio: g. Temnogametum Vegetative cells with 2 parallel flat chromatophores on opposite sides of the cell, each containing several pyrenoids; nucleus central in a cytoplasmic pillar between the flat sides of the 2 chromato- phores; conjugation between reflexed gametangia 10. Sirocladium Vegetative cells with 1 or 2 broad parietal chromatophores on one side of the cell, each with several pyrenoids, and laciniate lateral margins; in young cells the nucleus is near the middle of the single chromatophore, in mature cells in bridge between the 2 chroma- tophores; reproduction unknown..... 11. Entransia TAXONOMIC CHARACTERISTICS II VI. Vegetative cells with 1 to 16 parietal, more or less spirally arranged ribboniike chromatophores, each with several or many pyrenoids arranged in a single median line; nuclei centrally located and sup- ported by cytoplasmic strands; zygospores ellipsoid, ovoid, or len- ticular, always formed in one of the gametangia 1. With conjugating tubes formed by one or both gametangia before conjugation; outer layer of vegetative cell walls of pectic compounds, which usually disappears during conjugation 12. Spirogyra 2. Without conjugating tubes, conjugation directly through an opening where the reflexed gametangia are in contact; this area of contact becomes encircled by a ring of pectic compound; vegetative cells without a pectic sheath, chromatophores only SHEL iemnvcdnn vaca ca dele es rs 13. Sirogonium OTHER SUMMARIES OF THE ZYGNEMATACEAE Vaucher, J. P. 1803. Conjuguées. Histoire des Conferves d'eau douce. Geneva, pp. 37-81. Agardh, C. A. 1824. Systema Algarum. Lund. Hassall, A. H. 1845. History of British Freshwater Algae. London. Bary, A. de. 1858. Untersuchungen tiber die Familie der Conjugaten. Leipzig. Palla, E. 1894. “Ueber eine pyrenoidlose Art und Gattung der Con- jugaten.” Berichte deutsch. bot. Gesells. 12, p. 228. West, G. S. 1916. “Zygnemaceae.” Algae. Cambridge Botanical Handbooks. 1, pp. 331-53. Oltmanns, Fr. 1922. “Zygnemaceae.” Morphologie der Algen. Jena, 1, pp. 87-106. Skuja, H. 1929. “Stisswasser Algen von den westestnischen Inseln.” Acta Horti Bot. Univ. Latviensis. 4, pp. 38-49. Czurda, V. 1932. Zygnemales. Siisswasserflora Mitteleuropa. 9. Smith, G. M. “Zygnemataceae.” Freshwater Algae of the United States. pp. 536-57. Transeau, E. N. 1934. “Genera of the Zygnemataceae.” Trans. Amer. Micros. Soc. 53, pp. 201-7. Fritsch, F. E. 1935. “Zygnemoideae.” Structure and Reproduction of the Algae. pp. 316-37. Czurda, V. 1937. Conjugatae. Handbuch der Pflanzenanatomie. 6. Kolkwitz, R., and Krieger, W. 1941-44. Zygnemales. Rabenhorst’s Kryptogamenflora von Deutschland und der Schweiz. 13, abt. II. (Keys to genera and species. Contains most complete bibliography, lists of obsolete names, and alleged synonyms.) 12 ZYGNEMATACEAE TABLE I SUMMARY OF THE OBSERVED UsuaL Metuops oF REPRODUCTION AMONG THE ZYGNEMATACEAE ZYGOSPORES Conjugation Total APLAN- Jug Number AKINETES ae ; of : Scalariform : Scalariform Species and Lateral PURUETIE Ha cee oss Zygnemopsis ...... EA GUASII atte iy aie a's ot Zygogonium ...... Pleurodiscus ....... Mougeotiopsis ..... DEDUYE Ss rciisisis toss s Mougeotia ........ Temnogametum Sirocladium ....... ENTGUSG | cteicio ceteteis SPUIOLITA! jonieis elvis ci Sirogonium ....... OrOsG-O1o eo) CO .o oono OC OC KF OO OW me on: TOTAUSHi ss or ae Of the 494 species that usually reproduce by zygospores, 77 some- times also reproduce by aplanospores. These species are distributed as follows: Spirogyra, 25; Mougeotia, 25; Zygnema, 16; Zygnemopsis, 53 Zygogonium, 2; Debarya, 1; Temnogametum, 2; and Sirocladium, 1. CHAPTER TWO THE GENUS ZYGNEMA C. A. AGARDH 1824 The plants classified as species of Zygnema consist of un- branched filaments of short cylindric cells usually covered by a pectose sheath. To the field collector they are less slippery than the Spirogyras but more slippery than the Mougeotias. There are exceptions, of course, because the sheaths vary in thickness from those which are barely visible under the microscope to those which are thicker than the cells themselves. In regions of low tempera- ture and alkaline water, the sheaths are denser and highly stable. Similar sheaths are found on filaments living on wet shaded soil on pond margins. The thicker sheaths often have visible struc- tural lines at right angles to the filaments. Zygnemas live as annuals, and may complete their life cycle in a few weeks and then disappear. They are most abundant and more frequently found reproducing in temporary ponds and ditches. In permanent ponds one may find vegetative filaments throughout the year. This is not to be construed as evidence that individual plants are perennial. It is far more probable that the germination of spores and akinetes occurs throughout the year. In cold temperate regions the most abundant germination starts in autumn and winter, and culminates in early spring. As ponds become shaded by the growth of marginal shrubs and trees, repro- duction decreases and finally ceases entirely, but the Zygnemas are perpetuated for a subsequent period of years by the overwin- tering of akinetes and fragments of filaments. They survive cold and dry periods in the ooze and silt of the pond bottom. During the drought period between 1930 and 1935 a small pond near Columbus, Ohio, was dry for three and a half years. When the rains finally restored the pond, filaments of Zygnema sterile be- came abundant within three weeks. This species reproduces by akinetes only. Zygnemas have been collected on all the continents from sea level to alpine summits, and from the torrid to the frigid zones. 13 14 ZYGNEMATACEAE In higher latitudes and altitudes the species are not well known because they rarely have been found with zygospores. In warm regions it is not improbable that some species are perennial; that is, some of the filaments form spores and die, while others merely break into segments which continue vegeta- tive growth. In well-aerated running water the Zygnemas are rarely found fruiting, but in the shallow pools adjoining such streams one can usually collect the same species in a fruiting condition. The average length of the filaments of Zygnemas is a few inches, much shorter than that of the Spirogyras. Apparently before the filaments become very long the pectic sheath breaks and the cells separate. Cell diameters vary from 8 to 58, but more than half the species have cell diameters between 20 and 302. Usually there are two axial chromatophores in each cell with the nucleus contained in the cytoplasmic bridge connecting them. Each chromatophore consists of a round body, with irregular short branches radiating in all planes, containing a conspicuous central pyrenoid. As a result of food accumulation the chromatophores may become merely two large globose bodies, or may completely fill the lumen of the cell. On rare occasions one may find filaments in which each cell has two axial chromatophores on either side of the nucleus. In three collections that I have examined there were four chroma- tophores in the cells of some filaments arranged in the form of an X with the nucleus in the center. Sexual reproduction occurs in 82 of the 95 described species. Twelve others reproduce by aplanospores, and 1 by akinetes only. Of the described species reproducing by zygospores 37 are isog- amous, with spores in the conjugating tubes; and 45 are ani- sogamous, with spores in one of the gametangia. Of the 95 species, 40 have scalariform conjugation, 9 both scalariform and lateral conjugation, and 3 lateral conjugation; no conjugation has been observed in the remaining species. Thirty species have blue median spore walls when mature. During development these walls change from colorless to yellow, to brown, to blue. As not all spores mature at the same time, one may find all these stages in a collection. If some of the spores are blue, one may be sure that the other spores in the filament are immature. Four chromatophores are usually visible in immature zygo- ZYGNEMA 15 spores, and in parthenospores and aplanospores only two. In general the zygospores are compressed-globose or ovoid. There is an equatorial suture often marked by a slight ridge or keel (carinate), and in some species there are two lesser ridges on either side of the suture and parallel with it. These may not be visible in fresh fully distended spores but they become evident in dried or plasmolyzed specimens. Usually, the polar, or flatter, sides of the spores lie in the plane of the tubes, but there are 6 species in which the plane of compression is at right angles to the axis of the tubes. The most abundant and generally distributed of the brown- spored isogamous species is Z. pectinatum, of the blue-spored isogamous species, Z. synadelphum. Of the anisogamous brown- spored species Z. stellinum is both abundant and widely distrib- uted; Z. peliosporum is its counterpart among the blue-spored species. As might be expected, all these species are highly variable in dimensions, and local varieties and forms are apparently com- mon. It is not improbable that they have been the mutating fore- runners of nearly related species found locally wherever the Zygnemas have been studied intensively. There is no good evidence that the taxonomic characteristics of species are changed materially by environmental conditions. There are alterations in chromatophores, accumulated foods, and thickness of walls due to exposure on soil, restricted photosyn- thesis, low temperatures, and mineral deficiencies. Reproductive capacity may be decreased or increased by external conditions. The mode of reproduction by zygospores or aplanospores, and the placement of the zygospores in the tubes, or in one of the gam- etangia, are the results of hereditary rather than environmental factors. In any one species the position of the spores, whether in the tubes or in the gametangia, does not change from season to season (see Fritsch and Rich, New Phytologist, 26 [1927]). There are several species in which the spores occur in either the gametangia or the tubes—even in the same pair of conjugating filaments. The identification of a species depends partly upon the dimen- sions of the vegetative cells. Vegetative cell diameters should be measured at the partition walls. Most important are the relative dimensions of the spores, their form, and the color and ornamen- tation of the several layers of the spore walls. Obviously only 16 ZYGNEMATACEAE specimens with mature spore walls can be named with any degree of satisfaction. Not infrequently the ornamentation can be deter- mined only by crushing and separating the several layers of the spore wall. In the matter of dimensions, the student should remember that every species is a complex of clones with cells of slightly different sizes and proportions. These may be in part smaller or larger than the dimensions given in the key. The dimensions given in the descriptions of species are either those of the original collection, or the dimensions as they may have been modified by the study of subsequent collections. How great a departure from the original is necessary to warrant the segre- gation of a new species cannot be determined by any simple rule. Study and restudy of many collections will show that some species are only narrowly variable, while others vary within wide limits. These remarks are equally applicable to the species of other genera of the Zygnemataceae. In the descriptions of species the characteristics of the outer spore wall are usually omitted since there are only a few species in which they are not thin, smooth, colorless, and transparent. The median spore wall may be variously colored and ornamented. I have tried to distinguish among punctate, scrobiculate, and pit- ted according to the size of the pits, and in many instances have been able to give the diameters of the pits and the distances be- tween them in microns. Errors sometimes occur in descriptions and figures where contraction ridges and irregular folds are mis- taken for ornamentation. These may be due to contraction of the spore contents either by drying or by plasmolysis, and may be recognized readily by applying a dilute solution of potassium hydroxide. Real structural patterns are enlarged and made more distinct by this treatment, while contraction ridges disappear. In studying dried specimens it is well first to wet them with water on the slide and then to apply a drop of lactic acid, and after that to heat the slide until the acid begins to boil. This treatment will remove calcium carbonate and clarify both the walls and cell contents of most species. Some of the older species were described as having smooth median spore walls, although recent study of the type specimens has shown them to be punctate. This circum- stance is probably explained by the poor resolving power of the microscope lenses of the last century as compared with those available today. ZYGNEMA It may be of histuric interest to know that certain species of Zygnema have been classified previously in the genera: Globulina Link 1820; Tendaridea Bory 1822-31; Stellulina Link 1833; Tyndaridea Hassall 1841; Zygogonium Kutzing 1843; and Thwaitesia Montagne 1845. More recently Czurda (1932) has included among the Zygnemas certain species which are here classified in the genera: Zygogonium, Zygnemopsis, Hallasia, and Pleurodiscus. Key To Sprcires or ZYGNEMA 1. With aplanospores, zygospores infrequent or absent.......... 53 1. With zygospores, sometimes aplanospores also............... 2 2. Zygospores wholly or largely in the conjugating tubes.... 3 2. Zygospores usually in one of the gametangia............. 26 3. Median spore wall colorless, yellow, or brown when mature.. 4 peMedian: spore wall blue when matures (i)... s.j. co.cc sea: = 17 As Ay eOSPOrES: PlOWOSE tTO,OWVOIG 2, ce ie. seals is tiectace & See Mes 5 4. Zygospores compressed, at right angles to the tubes....... 22 Bay oiameter veoetative cells less! cham amis .3. 43. See 3. edie o's 6 5. Diameter vegetative cells usually 20 toi 20M..3 26.645 2 6a Sear 8 5. Diameter vecetative cells usually 20\to 40 pe. os. joj. ot shes 15 B. iameter, verctative cellssmore than: agp. cc. . 0 oie a.\)4 late sea oe 16 6. Vegetative cells 8-12 in diameter. 1. Z.oveidanum GO» Veocidiive cells 12-16 yn) Ir Cianieters s).ae alae viele Neleuye ns ae 7 6. Vegetative cells 16-20» in diameter, SPORES, SCrObIGUlate ose noha tie’ 4. Z. decussatum 6. Vegetative cells 16-20» in diameter, SHOLES! SIIOOEN baton 1.5) les eles gt. Z. gangeticum 7. Median spore wall scrobiculate....... 2. Z. carterae 7. Median spore wall smooth. :.......... 3. Z. laevisporum Silviecianesporeswallia sinele layers .6)\ 6224.62 os ace cle dase 9 Oaniedian spore walllor ailayersi iis... <'s 582+ yan somata s 14 g. Zygospore median wall smooth....... 23. Z. czurdae g. Zygospore median wall scrobiculate, pits less than 4u......... 10 g. Zygospore median wall scrobiculate, pits more than 4p....... 13 g. Zygospore median wall reticulate..... 14. Z. pseudopectinatum 10. Diameter cells 20-22, lateral con- jugation through end walls....... 5. Z. himalayense 10. Diameter cells 20-30, conjugating tubes of usual form... 11 11. Spores usually less than gop in diameter.................055 12 18 II. T2. 13. ZYGNEMATACEAE Spores usually more than 4op in diam- eter 12. Spores 24-331, scrobiculate, diam- eter pits less than 2f60): v5250 sesso . Spores 33-40/4, scrobiculate, diam- Pet OMS 2A) 5 aoe aes . Spores 38-42 /4, punctate and ridged . Spores 36-451, scrobiculate, diam- Gter Pits 2 hyo aio se dak ae onda) Diameter median spore wall pits 5-8. Diameter median spore wall pits 41... 14. Outer layer wrinkled, inner verru- oe ame ORI UAE Faas Od) it eae rucose 14. Outer layer pitted, inner verrucose. > 4's 8b .61e sD. 8,9) s) be #6, ble a Pee ese Oe . Median spore wall single, pits 2-3 in diameter a ar DIOR Wa ey Wh der te het So 8 BC ay . Median spore wall single, pits 3-4 in diameter . Median spore wall double, outer ver- rucose 16. With median spore wall single.... 16. With median spore wall double... SN Le in Ft he ih at va) te Yet de (St es ee CO . Z. skujae . Z.conspicuum . Z.lawtonianum . Z.chungi . Z.adpectinatum . Z. sinense . Z. globosum . Z. verrucosum . Z. laetevirens . Z. areolatum . Z. pectinatum . Z.excrassum . Z. verrucosum 19. 20. Z. neopectinatum Z. giganteum 17. Diameter vegetative cells 16 or less.. 21. Z. gedeanum 27. i diameter ‘vegetative cells’ 17-27 hina, iv. eae ote. ee 18 x7, Diameter vegetative cells:more than 278.0)... ..:¢.5.senems 21 8, Median ‘wall smoothi.)oycicis' 4 tS coin eee ouee ae 19 16, Median wall hat ‘amaoth:....+.aarackouauenmes «saute ee 20 19. 19. Median spore wall dark blue, diameter 34-40 b Median spore wall light blue, diam- eter 30-40 /4 Diameter vegetative cells 16-18», spores compressed Diameter vegetative cells 17-24}. . Diameter vegetative cells 24-26, diameter spore 32-35 4 Diameter vegetative cells 23-27», diameter spore 36-424 Diameter vegetative cells 18-24, forming mats on soil............. 20. 20. 20. 20. 20. 22. 23. Z.cyanosporum Z. czurdae . Z. carinatum . Z.synadelphum . Z.coeruleum . Z. gorakhporense . Z. terrestre ZYGNEMA 21. Vegetative cell diameter 27-30p...... 28. Z. majus 21. Vegetative cell diameter 32-38m...... 29. Z. kiangstense 22. Zygospores blue, carinate, and PURetale hy iya co usa eas Sieie 35. Z. carinatum 220 Lyeospores yellow. to brow. : (Sts joc vee nis yee tas « 23 ae eiameter vegetative cells T4-2Op)... 0)... cas ca ejaaiae sit deb s) 80. Z. frigidum 54. Spores scrobiculate, diameter vege- tative cells 2p se eathitene tts. 85. Z. hypnosporum 54. Spores sioGth..i:3.' nists shins 25's 84. Z. quadrangulatum 55. Diameter vegetative cells less than 25#.........--++e++eeeeee 56 55. Diameter vegetative cells 26 to 364..........-.02seeeeeeeeeee 57 55- Diameter vegetative cells greater than 36}..............0055 58 56. Vegetative cell diameter 15-18», spores dolioform .........+.-+++++: 94. Z. mirificum 56. Vegetative cell diameter 16-214, SDOFES DVO <)5.50 4'dns oh a9 yee a 81. Z. spontaneum 56. Vegetative cell diameter 17-20/, SROres CYUMBATIC fos aie glee ve 86. Z. schwabei 56. Vegetative cell diameter 20-22, spores ellipsoid .).... saan enielse aur 93. Z. ellipsoideum 57. Median spore wall scrobiculate....... 82. Z. cylindricum 57. Median spore wall granulose......... 88. Z. subcylindricum 57. Median spore wall pitted............. 95. Z. khannae 58. Diameter vegetative cells 40-42, pore Cy MMCNe . Fi. ees cae cian: 89. Z. irregulare 58. Diameter vegetative cells 44-54H, NMIUBEES v5 ies sh 3 vn v-dine sien ed eee 83. Z. sterile The following species have been found in some collections produc- ing both zygospores and aplanospores: Z. catenatum, Z. circumcart- natum, Z. collinsianum, Z. cruciatum, Z. excrassum, Z. fanicum, Z. giganteum, Z. insigne, Z. leiospermum, Z. neocruciatum, Z. pecti- natum, Z. peliosporum, Z. stellinum, Z. terrestre, and Z. synadelphum. DeEscRIPTIONS OF SPECIES 1. ZYGNEMA OVEIDANUM Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 208, Pl. 17, Fig. 1. Vegetative cells 8-12 « x (32-) 35-40(-68) #; conjugation scalariform; zygospores formed in the conjugating tubes, ovoid to globose, 12-15 x 15-30; median spore wall colorless to yellow, punctate; pits about 14 in diameter. (PI. II, Fig. 3.) ZYGNEMA 23 United States: Florida, Oveida Springs, and Fort Myers; Louisiana, Alexandria. 2. ZYGNEMA CARTERAE Czurda 1932. Susswasserflora Mitteleuropa. g, p- 114. Carter. Jour. Linn. Soc. of London Bot. 46, p. 62. Vegetative cells 13-16 in diameter; conjugation lateral or scalari- form; zygospores formed in the conjugating tubes, globose, 30-35; median spore wall brown, scrobiculate. New Caledonia (Carter). 3. ZYGNEMA LAEVISPORUM Jao 1935. Trans. Amer. Micros. Soc. 54, p. 56, Pl. 1, Figs. 7-8. Vegetative cells 13-164 x (48-)64-128 4; chromatophores usually 2, sometimes 3 or 4, occupying the middle of the cell; conjugation usually lateral, rarely scalariform; zygospores compressed-globose, formed in the conjugating tubes, 35-42“ x 32-354; median spore wall smooth and yellow-brown at maturity. (Pl. H, Figs. 5-6.) United States: Massachusetts, Falmouth. 4. ZYGNEMA DECUSssATUM (Vaucher) Agardh 1824. Systema Al- garum, p. 78. Vegetative cells 16-20" x 35-100 (2-5 diameters long); conjuga- tion scalariform; zygospores formed in the conjugating tubes, globose to ovoid, 24-334 x 26-364; median spore wall brown, finely scrobicu- late. (PI. II, Fig. 7.) United States: Illinois; Indiana; Michigan; Massachusetts. Widely reported from Europe; India; New Caledonia. This form is not identical with Zygnemopsis decussata Transeau as transferred by Czurda. Both species have been found in the same pond. Their reproductive structures are quite dissimilar. (See Pl. IX, Figs. 12-15.) 5. ZYGNEMA HIMALAYENSE Randhawa 1940. Proc. Indian Acad. Sez. 82, pi 120. Vegetative cells 20-224 x 60-120; conjugation lateral and scalari- form. In lateral conjugation the gametes unite directly after solution of the wall between the gametangia. Zygospores formed in the conju- gating tubes in scalariform conjugation; spores subglobose to ovoid, 36-40 X 45-72; median spore wall scrobiculate, yellow-brown; pits I-1.5 in diameter, 3-4 apart. (Pl. II, Fig. 4.) India, Loharkhot, stream at an elevation of 5,750 feet in the Himalaya Mountains, September 15, 1939. 6. ZYGNEMA CONSPICUUM (Hassall) Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 208, Pl. 17, Fig. 2. Vegetative cells 22-27 x 50-90; conjugation scalariform; zygo- 24 ZYGNEMATACEAE spores formed in the conjugating tubes, globose to ovoid, 24-32 x 26-33; median spore wall brown, scrobiculate; pits about 1.5-2.0" in diameter and the same distance apart. (Pl. I, Fig. 8.) United States: Illinois; Wisconsin; Oklahoma; Kentucky. England; Germany; Austria; Belgium; Bulgaria; Russia. 7. ZYGNEMA SKUJAE Czurda 1932. Séisswasserflora Mitteleuropa. g, p. 109. Skuja. Acta Horti Bot. Univ. Latviensis. 4, p. 40. 1920. Vegetative cells 20-27 x 40-100; conjugation scalariform; gam- etangia slightly bent; zygospores formed in the conjugating tubes, globose to ovoid, 40-55; median spore wall olive-brown, coarsely and thickly scrobiculate. Latvia. 8. ZYGNEMA LAWTONIANUM Taft 1934. Trans. Amer. Micros. Soc. 53, p. 200, Pl. 17, Fig. 5. Vegetative cells 23-27 x 23-99; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose to ovoid-globose with a distinct equatorial suture, 33-40" x 33-46; outer spore wall united with the tube wall; median spore wall brown, coarsely scrobiculate; pits 3-4 in diameter and about the same distance apart. Spores are cut off from the gametangia by a distinct cross wall. (Pl. II, Fig. 9.) United States: Oklahoma, Medicine Park, April 29, 1932. Burma (Skuja). g. ZYGNEMA VERRUCOSUM Jao 1935. Sinensia. 6, p. 566, Pl. 1, Figs. 3-4. Vegetative cells 24-26 x 29-48; conjugation scalariform; zygo- spores formed in the conjugating tubes, subglobose to ovoid, 32-37" x 38-55; outer spore wall smooth, hyaline; median wall of 2 layers, of which the outer is yellow and irregularly wrinkled, the inner, yellow- brown and densely granulate to verrucose. (Pl. II, Figs. 10-11.) China, Szechwan. Differs from Z. pawhuskae Taft in the larger vegetative cells, the absence of a distinct suture on the spore, and the absence of compressed- ovoid spores. 10. ZyYGNEMA cHUNGI Li 1934. Trans. Amer. Micros. Soc. 53, p- 213, Pl. 18, Fig. 15. Vegetative cells 24-28 x 58-724; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose to ovoid, 38-42" x 38-47 4; outer wall colorless, smooth; median spore wall yellow-brown, ZYGNEMA 25 thick, punctate, and marked by an irregular network of ridges; pits about 1 in diameter, 3-6 apart. (PI. II, Fig. 12.) China, Hupeh, Wuchang (H. H. Chung Coll.). 11. ZYGNEMA SINENSE Jao 1935. Sinensia. 6, p. 567, Pl. 1, Fig. 5. Vegetative cells 25-27 x 25-48; conjugation scalariform; spores formed in the enlarged tubes, extending slightly into the gametangia; zygospores subglobose to ovoid, not compressed, 35-42 x 40-484; median spore wall brown, pitted; pits 5-8» in diameter, 3-gm apart. (Pi, IIL, Figs 1.) China, Szechwan. Differs from Z. lawtonianum Taft in larger zygospores, larger pits, and absence of distinct suture; from Z. areolatum Transeau in having a single median spore wall, larger pits, and smaller vegetative cells. 12. ZYGNEMA GLOBOSUM Czurda 1932. Sisswasserflora Mitteleu- ropa. 9, p. 109, Fig. 110. Vegetative cells 26-28 x 70-95; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose or ovoid, 45-50" x 50-65 4; median spore wall brown, thick, pitted; pits about 3 in diam- eter according to the figure. (PI. III, Figs. 2-3.) Bohemia; Central India. 13. ZYGNEMA ADPECTINATUM Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 209, Pl. 17, Fig. 6. Vegetative cells 25-30 x 30-100; conjugation scalariform; zygo- spores formed in the conjugating tubes, ovoid to globose, 36-40" x 40-50; median spore wall yellow-brown, scrobiculate; pits 24 in diam- Siena el) TS Fig. 4:) United States: Illinois. 14. ZYGNEMA PSEUDOPECTINATUM Czurda 1932. Sésswasserflora Mitteleuropa. 9, p. 115, Fig. 117. Fritsch and Stephens. Trans. Roy. Soc: S. Africa. 9, p- 53. 1921. Vegetative cells 27-304 x 50-74; conjugation scalariform and lateral; zygospores formed in the conjugating tubes, globose to ovoid, 33-36 x 40“; median spore wall brown, thick, reticulate. South Africa, Transkei. 15. ZYGNEMA AREOLATUM Taft & Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 210, Pl. 17, Fig. 8. Vegetative cells 27-30 x 46-66; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose to ovoid, 32-46" x 33-50; median spore wall brown, of 2 layers, of which the outer is 26 ZYGNEMATACEAE pitted; pits 5-6 in diameter, 1.5-3 apart, the inner layer densely and minutely verrucose. (PI. III, Fig. 5.) United States: Oklahoma. 16. ZYGNEMA LAETEVIRENS Klebs 1886. Untersuch. Bot. Inst. Tubingen. 2, p. 333, Pl. 3, Fig. 14. Vegetative cells 27-34 x 40-90; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose, 40-55 in diameter, or ovoid, 34-41 x 54-68; median spore wall chestnut brown, of 2 layers, of which the inner is finely verrucose, the outer scattered-scrobic- ulate. It is probable that the ornamentation of the inner median wall arises from granules formed between the 2 layers. The same may be true of Numbers 9 and 15. United States: Indiana; Ohio; Mississippi; Alabama. Europe; Australia; China (L. C. Li Coll.). Spores may be yellow before the verrucose markings of the inner median wall appear. The Indiana specimens contained many parthenospores similar to the zygospores but smaller. 17. ZYGNEMA PECTINATUM (Vaucher) Agardh 1817. Synopsis Algarum, p. 102. Vegetative cells 30-36 x 25-120; conjugation scalariform, rarely lateral; zygospores formed in the conjugating tubes, globose to ovoid, 35-44 X 40-54; median spore wall brown, scrobiculate; pits about 2-3». in diameter; aplanospores ovoid or cylindric, 30-384 x 30-604; walls similar. (Pl. III, Fig. 6.) United States: Generally distributed eastward from Minnesota, Ne- braska, Oklahoma, and Louisiana. Widely distributed in Europe, Asia, Africa, and South America. 18. ZYGNEMA EXCRASSUM Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 209, Pl. 17, Fig. 14. Vegetative cells 32-36" x 32-80; conjugation scalariform; zygo- spores formed in the conjugating tubes, usually ovoid, rarely globose (40-)50-60 x 50-70(-80)“; median spore wall brown, scrobiculate; pits 3-4 in diameter and about the same distance apart; aplanospores cylindric-ovoid, nearly filling the sporogenous cells. (PI. III, Fig. 7.) United States: Oklahoma; Illinois; Iowa; Mississippi; Alabama. 19. ZYGNEMA NEOPECTINATUM ‘Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 209, Pl. 17, Fig. 7. Vegetative cells 40-45 x 40-854; conjugation scalariform; zygo- spores formed in the conjugating tubes, ovoid to globose, 45-54" x ZYGNEMA 27 55-60; median spore wall brown, scrobiculate; pits about 3 in diam- erer. (PI.111, Fig. 8.) United States: Illinois. 20. ZYGNEMA GIGANTEUM Randhawa 1936. Proc. Indian Acad. Sct. 4 p. 241. Vegetative cells 40-48 x 56-go; reproduction by zygospores and aplanospores; conjugation scalariform; zygospores formed in the con- jugating tubes; zygospores ovoid to globose, 48-64 x 56-70; median wall yellow-brown, of 2 layers, of which the outer is undulate pitted and the inner smooth or granulate. The other 2 walls are transparent. Aplanospores cylindric, filling the cells, with walls similar to those of the zygospores, 38-48 x 45-72u. (Pl. II, Figs. 9-10.) India, Kapurthala State, Punjab, March, 1931. This description is modified from the original on the basis of specimens kindly sent by Mr. Randhawa. Associated with this species in the original collection is an anisogamous species with very peculiar conjugating tubes, in that a ring of pectic material surrounds the tube at the point of union. This is indicated by Randhawa’s figures. However, there are no ripe spores in the material that I have seen and because of the smaller zygospores | believe it is a distinct and unnamed species. 21. ZYGNEMA GEDEANUM Czurda 1932. Sisswasserflora Mittel- europa. 9, p. 115, Fig. 118. Vegetative cells 13-15 x 32-34; conjugation lateral; zygospores formed in the conjugating tubes, ovoid, 22-24 « x 30-324; median spore wall blue to blue-black, thick, pitted; pits about ru in diameter. (PI. III, Figs. 11-12.) Java. 22. ZYGNEMA CYANOSPORUM Cleve 1868. Nova Acta Reg. Soc. Sci. Upsali. 6, p. 28, Pl. 8, Figs. 6-8. Vegetative cells about 20-22 x 40-180; conjugation scalariform; zygospores formed in the conjugating tubes, globose, rarely quadrate- globose, 30-40 in diameter; median spore wall blue, thick, smooth. United States: Michigan. Greenland; Sweden; Finland; India; South Africa. 23. ZYGNEMA CZURDAE Randhawa 1936. Proc. Indian Acad. Sci. 4.10), 230, Vegetative cells 20-274 x 30-100, with 2 chromatophores; con- jugation lateral and scalariform; spores formed in the tubes; during lateral conjugation the intergametangial wall splits and the gametangia are connected only by the enlarged tubes; in scalariform conjugation the 28 ZYGNEMATACEAE spores are formed in the tubes; zygospores globose, 30-40 in diameter, all walls smooth and light blue in color. (Pl. II, Figs. 13-14.) India, Punjab, February, 1931. These spores may not be mature and the color may be due to refraction of light rather than the presence of a blue pigment. 24. ZYGNEMA SYNADELPHUM Skuja 1926. Acta Horti Bot. Univ. Latviensis. 1, p. 110, Pl. 1, Fig. 2. Vegetative cells 17-214 x 34-120; conjugation scalariform; zygo- spores formed in the conjugating tubes, ovoid to spheroid, 27-36" x 34-444; median spore wall blue, of 3 layers, of which the outer is irreg- ularly punctate; pits about 1-2 in diameter; suture sometimes prom- inent, usually not. Aplanospores cylindric-ovoid, filling the vegetative cells, otherwise similar to the zygospores. (Pl. IV, Figs. 1-2.) United States: Oklahoma; Texas; Michigan; Ohio; Louisiana; Florida. Latvia; China; Africa, Burma. In a collection from Alexandria, Louisiana, aplanospores were very abundant. In a collection from Florida most of the spores were in the tubes, but occasional spores were in the gametangia of both conjugating filaments. 25. ZYGNEMA TERRESTRE Randhawa 1938. Proc. Indian Acad. Sct. 8, p. 147, Fig. 29. Vegetative cells 18-24" x 36-604; conjugation scalariform, zygo- spores in the tubes or extending into the gametangia, subglobose to ovoid, 28-38 » x 36-54); median wall blue when mature, brownish when immature, punctate with pits 5-1 in diameter 3-5 apart; aplan- ospores ovoid to dolioform, formed in the enlarged middle part of the cells; the outer wall of the cell adjoining the spore changes to pectic compound forming a collar. When mature the aplanospore walls are similar to those of the zygospores. Aplanospores are 30-34 x 36-654. Some filaments have several of the lowermost cells with disintegrating chromatophores beneath the soil surface. (Pl. VII, Figs. 16-18.) India, Fyzabad, forming a light green felt on the soil surface of fallow fields at the close of the rainy season, late September and October, 1937. 26. ZYGNEMA COERULEUM Czurda 1932. Sisswasserflora Mittel- europa. 9, p. 107, Fig. 107. Vegetative cells 24-26 x 40-55 in diameter; conjugation scalar- iform; zygospores formed in the conjugating tubes, ovoid to globose, 32 X 32-354; median spore wall blue, thick, scrobiculate; pits 1.5 in diameter, 2 diameters apart. (Pl. IV, Figs. 3-4.) Bohemia; South Africa; northern India. ZYGNEMA 29 27. ZYGNEMA GORAKHPORENSE Singh 1938. Jour. Indian Bot. Soc. 17, p. 370. Vegetative cells 23-27 x 66-8314; conjugation scalariform; zygo- spores formed in the tubes and extending into the gametangia; zygo- spores ovoid to globose, 30-364 x 36-43; median wall blue, scrobic- ulate; pits about 4 in diameter and 1-3 apart. India, Gorakhpur, October 8, 1936. 28. ZyGNEMA Majus Czurda 1932. Sésswasserflora Mitteleuropa. 9, p. 106. Fritsch & Rich. Trans. Roy. Soc. S. Africa, 9, p. 50. ‘1g2r. Vegetative cells 27-304 x 27-9g0/; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose to ovoid, 33-48u x 42-504; median spore wall blue, smooth. Africa, Transkei Territory. 29. ZYGNEMA KIANGSIENSE Li 1938. Bull. Fan Mem. Inst. Biol. 8, p. 94. Vegetative cells 32-38 x 36-50; conjugation scalariform; zygo- spores formed in the conjugating tubes, ovoid to subglobose, 36-46 x 44-5814; median spore wall blue, coarsely scrobiculate; pits 3-5 in diameter, 4-7 apart. (PI. IV, Fig. 5.) China, Kiangsi. 30. ZYGNEMA RALFSt (Hassall) de Bary 1858. Untersuchungen tiber die Familie der Conjugaten, p. 77. Vegetative cells 14-20. x 38-80; conjugation scalariform; zygo- spores formed in the conjugating tubes, 15-25 x 25-35; median spore wall brown, smooth. (PI. IV, Fig. 6.) United States: Pennsylvania, Harrisburg (Wolle). British Isles and continental Europe. 31. ZYGNEMA MICROPUNCTATUM Transeau 1934. Trans. Amer. Micros: Soc: 33, p. 210, Pl.-17) Fig..13) Vegetative cells 14-16 x 24-52; conjugation scalariform; zygo- spores formed in the greatly enlarged conjugating tubes, compressed- globose, with the longer diameter at right angles to the conjugating tube, 28-32 x 36-404; median spore wall yellow-brown, minutely and densely punctate. (Pl. IV, Fig. 7.) United States: Michigan; Oklahoma. 32. ZYGNEMA MOMONIENSE W. West 1892. Jour. Linn. Soc. of London Bot. 29, p. 114, Pl. 24, Fig. 26. Vegetative cells 20-22 » in diameter; conjugation scalariform; zygo- 30 ZYGNEMATACEAE spores formed in the conjugating tubes, compressed-globose, with the longer diameter at right angles to the conjugating tubes; 25-27" x 30-33/; median spore wall [?] brown, smooth. Ireland. 33. ZYGNEMA CIRCUMCARINATUM Czurda 1930. Beth. Bot. Zen- tralbl. 47, p. 53, Fig. 15. Vegetative cells 20-22 in diameter; conjugation scalariform; zygo- spores formed in the conjugating tubes, globose or compressed-globose, 24/4 to 29 in diameter; median spore wall golden-brown, thick, scro- biculate, with pits 2-2.5 in diameter and 1-2, apart; spore wall more or less carinate. As the spores mature the tube walls change to pectic compounds and form persistent colloidal walls as thick as the spores themselves. This often results in separation of the spores from their subtending gametangia. Aplanospores similar but smaller, often maturing outside the sporogenous cell. (Pl. IV, Figs. 8-9.) United States: Texas, Eden, April 13, 1938 (Taft Coll.). Bohemia. In Handbuch der Pflanzenanatomtie (6, Conjugatae) Czurda discusses and figures stages in conjugation, and germination of spores of this species, which he had cultivated. Exactly similar stages in spore maturation occur in several species of Mougeotia (P|. XVII). Note that the spores are also of the compressed type. 34. ZYGNEMA PAWHUSKAE Taft 1934. Trans. Amer. Micros. Soc. 53, p. 200, Pl. 21, Fig. 61. Vegetative cells 21-24 x 40-60; conjugation scalariform; zygo- spores formed in the conjugating tubes, ovoid to compressed-globose, extending into the gametangia, 34-48 x 46-65; median spore wall seal-brown, of 2 layers, the outer smooth with a distinct equatorial suture, the inner densely and minutely verrucose, sometimes reticulate- verrucose. During the early stages of conjugation the outer sporangium wall is a pectic layer 3-6» in thickness. (PI. IV, Fig. 10.) United States: Oklahoma. 35. ZYGNEMA CARINATUM Taft 1934. Trans. Amer. Micros. Soc. 53, p. 210, Pl. 17, Fig. 9. Vegetative cells 16-18 x 33-364; conjugation scalariform; zygo- spores formed in the conjugating tubes, compressed-globose, with the longer axis at right angles to the conjugating tube, 23-26" x 29-331; median spore wall blue, punctate, and encircled by a prominent suture. During development the sporangium wall is encased in a pectic layer 3-6 in thickness. (PI. IV, Fig. 11.) United States: Oklahoma. ZYGNEMA 31 36. ZYGNEMA STAGNALE (Hassall) Kutzing 1849. Species Algarum, Pp. 444- Vegetative cells g-12 x 20-50; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia enlarged on the inner side; zygospores globose to subglobose, 14-18 x 14-20; median spore wall brown, punctate. United States: Massachusetts, North Eastham (Collins Coll.). England. 37. ZYGNEMA SUBTILE Kitzing 1849. Species Algarum, p. 444. Vegetative cells 14-20" x 30-851; conjugation scalariform or very rarely lateral; zygospores in one of the gametangia; receptive gam- etangia greatly enlarged or inflated on the inner side; zygospores ovoid to subglobose, 20-29 » x 22-304; median spore wall brown, punctate. United States: Illinois. Finland; Germany; Bohemia. This is possibly the species figured by G. S. West (1909) as Z. spon- taneum from Yan Yean Reservoir, Australia. In a collection from Calhoun, Illinois, in a filament of 35 cells there were 11 gametangia with scalariform conjugation, 2 pairs conjugating laterally, and 20 vegetative cells scattered among them. 38. ZYGNEMA CYLINDROSPERMUM (W. & G. S. West) Krieger 1941. Zygnemales. Rabenhorst’s Kryptogamenflora. 13, p. 260. Vegetative cells 15-18» in diameter; conjugation scalariform; zygo- spores formed in one of the gametangia; receptive gametangia cylindric or slightly enlarged; zygospores ovoid, 15-19 x 23-54; median spore wall brown, punctate. (PI. IV, Fig. 16.) Shetlands (Loch Asta); Wales (Wittrock and Nordstedt No. 750); Cape Colony (Stephens Coll.). 39. ZYGNEMA YUNNANENSE Li 1940. Bull. Fan Mem. Inst. Biol. 10, p. 63. Vegetative cells 16-18 x 50-104; conjugation lateral; receptive gametangia more or less enlarged; zygospores globose to ovoid, 32-40 x 38-48; median wall thick, deeply scrobiculate, with pits 3-4.5 in diameter, 2-34 apart, yellow at maturity. China, Yiinnan, October 1, 1938. 40. ZYGNEMA EXTENUE Jao 1935. Sinensia. 6, p. 568, Pl. 1, Fig. 8. Vegetative cells 19-25 x 32-48; conjugation scalariform and sometimes :lateral; receptive gametangia more or less enlarged; zygo- spores subglobose to. ovoid, 23-32 x 26-39; median spore wall scro- 32 ZYGNEMATACEAE biculate; pits 4.5-6.5 in diameter and 2-3, apart, yellow-brown at maturity. (Pl. IV, Fig. 12.) China, Szechwan. 41. ZYGNEMA THOLOSPORUM Magnus & Wille 1884. Sydamerica Algflora, p. 33, Pl. 1, Figs. 49-52. Vegetative cells 20 x 20-40; conjugation scalariform; zygospores in one of the gametangia; receptive gametangia inflated; zygospores globose, 36 in diameter; median spore wall brown, with numerous circular prominences (umbonate). (PI. IV, Fig. 13.) Uruguay, Montevideo. 42. ZYGNEMA TENUE Kutzing 1849. Species Algarum, p. 445. Vegetative cells 18-24 x 20-70; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia greatly enlarged or inflated toward the middle; zygospores globose to ovoid, often some- what compressed, 25-30 x 25-40/4; median spore wall brown, scrobic- ulate; pits 2-3 in diameter, 3-4» apart. (Pl. IV, Figs. 14-15.) United States: Illinois; Oklahoma. Europe, widely reported; North and South Africa; China; Ceylon. 43. ZYGNEMA LEIOSPERMUM de Bary 1858. Untersuchungen tiber die Familie der Conjugaten, p. 77, Pl. 1, Figs. 7-14. Vegetative cells 20-244 x 20-40; conjugation scalariform; zygo- spores in one of the greatly enlarged or inflated gametangia; zygospores globose to ovoid, 23-30 x 23-324; median spore wall brown, smooth; aplanospores similar, but smaller in diameter. United States: Minnesota and Illinois to the east coast. Greenland; Iceland; British Isles; continental Europe. 44. ZYGNEMA HAUSMANNII (De Notaris) Czurda 1932. Sisswasser- flora Mitteleuropa. 9, p. 121, Fig. 125. Vegetative cells 21-23 x 34-72; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia enlarged mostly on the inner side; zygospores globose or slightly compressed, 32-34" x 28-34); median spore wall yellow-brown, pitted; pits 7-9» in diam- eter; equatorial suture distinct. (Pl. IV, Figs. 17-18.) Austria; northern Italy; southern Australia. 45. ZYGNEMA SUBSTELLINUM Taft 1934. Trans. Amer. Micros. Soc. 53, p. 212, Pl. 17, Fig. ro. Vegetative cells 22-24 x 50-70"; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia greatly enlarged, becoming nearly globose; zygospores globose, filling or nearly filling ZYGNEMA 33 the gametangia, 42-46. in diameter; median spore wall yellow-brown, scrobiculate; pits 3 in diameter. (PI. V, Fig. 1.) United States: Oklahoma, Bartlesville, April 25, 1932. This species is remarkable for the large size of the zygospores as com- pared with the size of the vegetative cells. 46. ZYGNEMA LUTEOSPORUM Czurda 1932. Séisswasserflora Mittel- europa. 9, p. 122, Fig. 225. Vegetative cells 22-24 x 45-80/4; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or slightly enlarged; zygospores ovoid, 26. x 38»; median spore wall yellow, thick, scrobiculate, with pits widely spaced. (Pl. V, Fig. 2.) Bohemia. 47. ZYGNEMA FLAVUM Taft 1946. Trans. Amer. Micros. Soc. 65, p- 24. Vegetative cells 22-274 x 48-68; conjugation scalariform; zygo- spores formed in one of the gametangia; receptive gametangia cylindric or slightly enlarged; zygospores cylindric-ovoid to ovoid, 24-29" x 35-5144; outer spore wall thin and smooth; median spore wall of 2 layers, the outer thick and smooth, the inner irregularly verrucose; both layers light yellow; innermost spore wall thin, smooth. (Pl. V, Fig. 3.) United States: Texas, Eden, April 13, 1938. In this collection some of the vegetative cells contained 4 chromatophores. 48. ZYGNEMA CALOSPORUM Jao 1935. Sznensia. 6, p. 568, Pl. 1, Pig7. Vegetative cells 23-26 x 16-48; conjugation scalariform; recep- tive gametangia shortened and greatly enlarged; zygospores globose to subglobose, 29-35 X 32-3543 median spore wall densely scrobiculate; pits 1.5-2.5u in diameter, 1-1.54 apart, yellowish-brown at maturity. (PIV, Fig. 4.) China, Szechwan. Differs from Z. substellinum Taft in greater diameter of the vegetative cells and smaller spores; from Z. vaucherii in shorter vegetative and repro- ductive cells, and in denser scrobiculations of the median spore wall. 49. ZYGNEMA vaucHERU Agardh 1824. Systema Algarum, p. 77. Vegetative cells 24-284 x 50-180; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia gradually or abruptly inflated toward the middle; zygospores ovoid, 24-36 x 26-45 13 median spore wall brown, scrobiculate; pits 2-3 in diameter. (Pl. V, Hig. 5.) 34 ZYGNEMATACEAE United States: Illinois; Indiana; Ohio; Massachusetts. Widely reported from Europe. 50. ZYGNEMA NORMANI Taft 1934. Trans. Amer. Micros. Soc. 53, p. 253; Pl. ‘17, Pig, 32: Vegetative cells 24-284 x 30-73; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia greatly inflated on the conjugating side; zygospores globose or subglobose, 36-46 x 35-45; median spore wall yellow-brown, scrobiculate; pits 3-4 in diameter, 2.5-4 apart. (Pl. V, Fig. 6.) United States: Oklahoma. India. 51. ZYGNEMA INSIGNISPORUM Couch 1944. Ohio Jour. Sct. 44, p- 277. Vegetative cells 24-28 x 39-71; conjugation scalariform; recep- tive gametangia inflated on the conjugating side; zygospores globose to ovoid, 32-35 X 32-35/4; outer wall of 2 colorless layers, of which the outermost is smooth, the inner scrobiculate, with pits 4-5 in diameter and about 7 apart; median wall punctate, yellow. United States: Arkansas. 52. ZYGNEMA VAGINATUM Klebs 1886. Untersuch. Bot. Inst. Tii- bingen. 2, p. 135, Pl. 3, Fig. 13. Notarisia. 1, pp. 340-41. 1886. Vegetative cells 25-27 x 37-75; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia slightly en- larged; zygospores globose to ovoid, diameter about 28; median spore wall brown, verrucose-tuberculate. Germany; Austria. Czurda (1932) and Krieger (1941) described this species as having scrobiculate median spore walls. No reason for the change from the original description is given. 53. ZYGNEMA SUBCRUCIATUM Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 212. Vegetative cells 24-30 x 26-60; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or enlarged, mostly on the inner side; zygospores globose to ovoid, 25-32 x 28-40; median spore wall brown, finely scrobiculate. (Pl. V, Fig. 7.) United States: Oklahoma; Texas; Arkansas; Louisiana; Illinois; Ohio. France; Norway; Sweden; China. ZYGNEMA 35 54. ZYGNEMA GERMANICUM Czurda 1932. Sésswasserflora Mittel- europa. 9, p. 125, Fig. 129. Vegetative cells 26-28 x 30-36; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia greatly enlarged or inflated; zygospores globose or compressed-globose, 36-38 ». x 36-45 #3 median spore wall brown, thick, pitted; pits 6-7 in diameter. (Pl. V, Figs. 8-9.) Germany; Czechoslovakia. 55. ZYGNEMA INSIGNE (Hassall) Kutzing 1849. Species Algarum, P: 444- Vegetative cells 26-32. x 26-60; conjugation scalariform or lat- eral; zygospores in one of the gametangia; receptive gametangia cylin- dric or enlarged; zygospores globose or subglobose, 27-33 x 27-35; median spore wall yellow-brown, smooth; aplanospores 28-33, ovoid to cylindric-ovoid, otherwise similar. (Pl. V, Figs. 10-12.) United States: California to Massachusetts and New Jersey. Widely reported from Europe, Australia, South America, and China. Many of the records of this species are based on specimens with imma- ture, colorless spores. These specimens should not have been named. 56. ZYGNEMA FANICUM Li 1934. Trans. Amer. Micros. Soc. 53, p. 212, Pl. 18, Figs. 17-19. Vegetative cells 28-334 x 28-80; conjugation usually scalariform, sometimes lateral; zygospores in one of the gametangia; receptive gam- etangia cylindric or enlarged; zygospores globose to ovoid, 30-36 x 34-42; median spore wall yellow, sharply pitted; pits 4-7" in diam- eter, 2-3 apart, each with a distinct, raised margin; aplanospores similar to zygospores. (PI. V, Figs. 13-14.) China, Hupeh, Kiangsi, Anhwei, Szechwan, Shantung. 57. ZYGNEMA SUBFANICUM Jao 1940. Sinensia. 11, p. 295, Pl. 4, Fig. 1. Vegetative cells 24-26 x 30-65, with 2 stellate chromatophores; conjugation scalariform; spores formed in one of the gametangia; re- ceptive gametangia enlarged on the conjugating side; zygospores glo- bose to subglobose, 29-35 4 in diameter; median wall pitted; pits 7-8» in diameter, 1.8-2.7 apart, yellow-brown in color. (Pl. V, Fig. 15.) China, Hunan. 58. ZYGNEMA TRANSEAUIANUM G. C. Couch 1944. Ohio Jour. Sci. 44, p. 27. Vegetative cells 30-32 x 20-60/4; conjugation scalariform; recep- tive gametangia enlarged or slightly inflated on the conjugating side; 36 ZYGNEMATACEAE zygospores globose to ovoid, 25-35 x 33-40“, somewhat compressed; median spore wall yellow-brown, reticulate, with large irregular pits 7-12 |4 across. United States: Arkansas, Boston Mountains. 59. ZYGNEMA STELLINUM (Vaucher) Agardh 1824. Systema Al- garum, p. 77. Vegetative cells 28-38 4 x 27-100”; conjugation scalariform, rarely lateral between occasional pairs of cells; zygospores in one of the gam- etangia; receptive gametangia inflated especially on the conjugating side; zygospores ovoid, 30-424 x 35-48(-57)#; median spore wall yel- low-brown, thick, scrobiculate; pits 3-4 in diameter, 3-4 apart; aplanospores common, usually cylindric, very rarely globose, the for- mer filling the sporogenous cells, the latter occupying the middle of the cells; spore walls similar to those of the zygospores. (Pl. I, Fig. 8; Pl. V, Fig. 16; and Pl. VI, Fig. 1.) United States: Washington and California eastward, very common in the central and eastern states. Canada; Greenland; Europe; Asia; South America; North Africa. 60. ZYGNEMA CRUCIATUM (Vaucher) Agardh 1817. Synopsis Al- garum, p. 102. Vegetative cells 30-36 x 30-60; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or enlarged; zygospores globose to ovoid, 30-384 x 32-40“; median spore wall brown, scrobiculate; pits 1.5-2 in diameter, 3-5 apart; aplan- ospores short, cylindric-ovoid, 30-35 x 30-60,, filling the vegetative cells, otherwise similar to the zygospores. (Pl. I, Fig. 9.) United States: Oklahoma; Iowa; Illinois; Massachusetts south to Mis- sissippi and Florida. Reported from all the continents. 61. ZYGNEMA CYLINDROSPORUM Czurda 1932. Stisswasserflora Mit- teleuropa. 9, p. 122, Fig. 126. Vegetative cells 31-364 x 60-80”; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or enlarged; zygospores short cylindric-ovoid to globose, 36-42 4 x 42-60 1; median spore wall yellow-brown, scrobiculate; pits about 1.5-2” in diameter, 3-5/4 apart; suture obliquely encircling the smaller circum- ference of the spore. (PI. VI, Fig. 2.) Macedonia; northern India; South Africa. 62. ZYGNEMA BOHEMICUM Czurda 1932. Sésswasserflora Mittel- europa. 9, p. 124, Fig. 128. ZYGNEMA 37 Vegetative cells 31-334 x 45-95; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or enlarged on the conjugating side; zygospores ovoid to cylindric-ovoid, 32-36. x 42-60"; median spore wall yellow-brown, thick, outwardly shallow pitted (visible only in section), and densely and finely verru- cose. (Pl. VI, Fig. 3.) Czechoslovakia. 63. ZYGNEMA MIRANDUM Taft 1946. Trans. Amer. Micros. Soc. 65, p. 24. Vegetative cells 28-35 x 32-64; conjugation scalariform; zygo- spores formed in one of the gametangia; receptive gametangia greatly enlarged on the conjugating side; zygospores compressed-globose to ovoid; median wall carinate; spore wall thin and smooth; median spore wall yellow-brown, of 2 layers, the outer thick and smooth, the inner reticulate, with the thin ridge crests irregularly broken; innermost spore wall smooth. (Pl. VI, Fig. 4.) United States: Texas, Austin and Fredericksburg, April 22-24, 1938. 64. ZYGNEMA INCONSPICUUM Czurda 1932. Sisswasserflora Mittel- europa. Q, p. 122, Fig. 127. Vegetative cells 36-394 x 50-70; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or scarcely enlarged; zygospores ovoid, sometimes extending into the en- larged tube, 404 x 50-60; median spore wall brown, pitted; pits 4-5 in diameter, 4-5 apart. (Pl. VI, Fig. 5.) Finland; Manchuria; northern India. See also Number 86. 65. ZYGNEMA NEOCRUCIATUM Transeau 1934. Trans. Amer. Micros. S06:,935 p: 212: Vegetative cells 40-50 x 30-100; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or slightly enlarged; zygospores globose to cylindric-ovoid, filling the gametangia, 40-45 x 40-50; median spore wall brown, scrobiculate; pits about 2 in diameter, 3-4 apart; aplanospores common and sim- ilar in size, rarely to 80 in length. United States: Illinois. Probably included in many records for Z. cru- ciatum elsewhere. See also Number 86. 66. ZYGNEMA CRASSIUSCULUM Transeau 1938. Amer. Jour. Bot. 20,'p.:524, Fig. 2. Vegetative cells 52-58 x 52-144; conjugation scalariform; zygo- 38 ZYGNEMATACEAE spores formed in one of the gametangia, compressed-globose to com- pressed-ovoid, 54-58 x 54-654 X 47-55; median spore wall brown, of 2 layers, of which the outer is scrobiculate; pits about 2 in diameter, the inner finely and irregularly verrucose. (Pl. VI, Figs. 6-7.) Africa, Cape Town (E. L. Stephens Coll.). 67. ZYGNEMA ATROCOERULEUM W. & G. S. West 1897. Jour. Roy. Micros. Soc. London, p. 476. Vegetative cells 14-17 x 40-70 in diameter; conjugation scalar- iform; zygospores in one of the gametangia; receptive gametangia en- larged or inflated; zygospores globose, 23-26(-29) » in diameter; me- dian spore wall dark blue, smooth. England. 68. ZYGNEMA CHALYBEOSPERMUM Hansgirg 1888. Hedwigia. 27, Pp. 253. Vegetative cells 24-27. x 24-84; conjugation scalariform or lat- eral; zygospores in one of the gametangia; receptive gametangia cylin- dric or enlarged; zygospores globose to ovoid, 30-334 x 30-384; median spore wall blue, thick, smooth. (PI. VI, Fig. 8.) United States: Illinois, Casey; Michigan (Ackley Coll.). Europe; Asia; North Africa. 69. ZYGNEMA CYANEUM Czurda 1932. Sisswasserflora Mittel- europa. 9, p. 127, Fig. 132. Vegetative cells 30-32 x 45-60; conjugation scalariform or lat- eral; zygospores in one of the gametangia; receptive gametangia cylin- dric or slightly enlarged; zygospores globose to cylindric-ovoid, 30-34" x 38-45; median spore wall blue, thick, smooth, (PI. VI, Figs. 9-10.) Bohemia; India. 70. ZYGNEMA COLLINSIANUM Transeau 1914. Amer. Jour. Bot. 1, p. 280, Pl. 25, Figs. 1-3, Vegetative cells 18-25 x 32-80; conjugation scalariform; zygo- spores mostly in one of the gametangia, sometimes in one filament, sometimes in the other, rarely in conjugating tube, extending into both gametangia; receptive gametangia enlarged on the conjugating side; zygospores globose to ovoid, sometimes slightly compressed and show- ing a distinct equatorial suture, 26-40" x 30-47; median spore wall blue at maturity, thick, pitted; pits 4-5 in diameter, 1-2 apart; aplan- ospores cylindric-ovoid, 18-24 x 40-76), scattered among the vege- tative cells, similar in markings to zygospores. (Pl. VI, Figs. 11-13.) United States: Oklahoma; Illinois; Indiana; Kentucky; Alabama. Northern India (Randhawa). ZYGNEMA 30 Named in honor of Frank S. Collins, author of Freshwater Algae of: the United States and many contributions to both marine and fresh-water algology. 41. ZYGNEMA MELANOSPORUM Lagerheim 1884. Bot. Zentralbl. 18) p. 270. Vegetative cells 22-27 x 36-100; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or slightly enlarged; zygospores ovoid to cylindric-ovoid, 23-30 x 28-36; median spore wall dark blue, finely punctate. United States: Ohio, Fayetteville, May, 1934. Sweden; North Africa. 72. ZYGNEMA EXCOMPRESSUM Transeau 1934. Trans. Amer. Micros. Soc. 95) p: 213, Vegetative cells 23-26 x 32-80; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia cylindric or enlarged; zygospores globose to subglobose, more or less compressed in the plane of the conjugating tube, 28 x 28-364; median spore wall blue, carinate, scrobiculate; pits 2.5-3 in diameter and about the same distance apart. (Pl. VI, Fig. 14.) United States: Oklahoma, Medford, April 26, 1932 (Taft Coll.). Bohemia. 73. ZYGNEMA PELIOSPoRUM Wittrock 1868. Bot. Noztiser. p. 190. Vegetative cells 23-30 x 24-80; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia enlarged, or in- flated on the conjugating side; zygospores globose to ovoid, slightly compressed, 28-36 x 28-46; median spore wall blue, finely scrobic- ulate or punctate, with pits 1-2 in diameter, spaced 2-3 apart; equa- torial suture usually distinct, sometimes prominent; aplanospores cylin- dric-ovoid, smaller and with similar markings. (Pl. VI, Fig. 17.) United States: California; Colorado; Texas; Indiana; Alabama. Sweden; Hungary; Spain; France; Norway; Finland; China. 74. ZYGNEMA AZUREUM Taft 1934. Trans. Amer. Micros. Soc. 53, p. 214, Pl. 17, Fig. 3. Vegetative cells 26-29" x 46-66; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia slightly to greatly enlarged; zygospores ovoid to cylindric-ovoid, 27-33 u x 33-504; median spore wall blue, finely punctate. (Pl. VI, Fig. 15.) United States: Oklahoma; Illinois. 75. ZYGNEMA CARINTHIACUM Beck 1929. Archiv f. Protist. 66, p. 1. Vegetative cells 25-30" x 25-100; conjugation scalariform; zygo- 40 ZYGNEMATACEAE spores in one of the gametangia; receptive gametangia much enlarged; zygospores globose to ovoid, 32-45 4 x 36-524; median spore wall blue, scrobiculate; pits 3-4 in diameter, 3-5 apart. (Pl. VI, Fig. 16.) United States: Oklahoma; Texas; Mississippi; Ohio; Florida. Austria; China. Forms with the same vegetative characters, but with smaller spores, have been collected in Ohio and Oklahoma. 76. ZYGNEMA PAWNEANUM Taft 1934. Trans. Amer. Micros. Soc. 53, p. 214, Pl. 18, Fig: 26. Vegetative cells 26-28 x 33-88; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia greatly enlarged on the inner side; zygospores globose, subglobose, or rarely ovoid, 36-46 4 x 36-48"; median spore wall blue when mature, pitted; pits 7-11. in diameter, 2-34 apart. (Pl. VII, Fig. 1.) United States: Oklahoma; Louisiana (Taft Coll.); Ohio; Florida (J. D. Smith Coll.). In the Ohio collection some of the spores were distinctly tricarinate. The pits may be round or somewhat angular depending upon the height of the ridges between the pits. 77, ZYGNEMA ORNATUM (Li) Transeau 1934. Ohio Jour. Sci. 34, p. 420. Li. Ohio Jour. Sci. 33, p. 153, Pl. 1, Figs. g-10. 1933. Vegetative cells 27-32 x 34-96; conjugation scalariform; zygo- spores in one of the gametangia; receptive gametangia enlarged on the inner side, or cylindric; zygospores globose, subglobose to ovoid, 28-38 « X 32-38); median spore wall blue, pitted; pits about 6 in diameter and about 2 apart. (Pl. VII, Fig. 2.) United States: Oklahoma; Louisiana; Mississippi; Alabama. China, Nanking (L. C. Li Coll.). 78. ZYGNEMA EXCOMMUNE Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 213. Czurda. Sésswasserflora Mitteleuropa. p- 119 (as Z. commune). Vegetative cells 30-32 x 55-90; conjugation scalariform; zygo- spores formed in one of the gametangia; receptive gametangia greatly enlarged on the conjugating side; zygospores globose to ovoid, 4o# x 50/4; median spore wall blue, thick, scrobiculate; pits about 2.5“ in diameter, about 4 apart, according to the figure. (Pl. VI, Fig. 3.) Bohemia. 79. ZYGNEMA CATENATUM Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 213. Vegetative cells 30-36 x 35-80; conjugation scalariform; zygo- ZYGNEMA 41 spores in one of the gametangia; receptive gametangia slightly enlarged on the conjugating side; zygospores globose to ovoid, slightly com- pressed, 30-364 x 30-46"; median spore wall blue, scrobiculate; pits I.5-2 in diameter, 2-4 apart; aplanospores similar, 30-34 x 30-80}, filling the cells. United States: Illinois. SPECIES REPRODUCING BY APLANOSPORES 80. ZYGNEMA FRIGIDUM Taft 1934. Trans. Amer. Micros. Soc. 53, p 214, Pl 27; Fig: 11. Vegetative cells 21-234 x 29-834; conjugation unknown; reproduc- tion by aplanospores, cylindric to tumid-cylindric with rounded ends, 22-24 x 24-44; median spore wall blue, scrobiculate; pits 1.5-2m in diameter, 3-4 apart. (Pl. 1, Fig. 6.) United States: Oklahoma; Texas. 81. ZYGNEMA SPONTANEUM Nordstedt 1878. De Algis et Characeis Sandwicensibus, p. 17, Pl. 1, Figs. 23-24. Vegetative cells 16-22 x 28-90; reproduction by aplanospores only; aplanospores ovoid to cylindric-ovoid, 18-22 x 22-324; median spore wall brown, scrobiculate; pits about 2 in diameter, 3-5 apart. (Pl. VII, Figs. 5-7.) Hawaii; South Africa (E. Stephens Coll.); Java (Czurda); China (Jao). At all the above stations this species produced only aplanospores. The illustrations, published by G. S. West (1909) under this name, showing scalariform conjugations are better illustrations of Z. subtle than of this species. Nordstedt’s original collection from Hawaii had cell diameters of 16-18 u; the South African material, 18-20; and the Szechwan specimens, 19-22 82. ZYGNEMA CYLINDRICUM Transeau 1915. Ohio Jour. Sci. 16, p..22. Vegetative cells 28-334 x 28-664; conjugation unknown; repro- duction by akinetes and aplanospores; aplanospores cylindric to tumid- cylindric, filling the cell, 30-33 x 24-54; median spore wall brown, scrobiculate; pits about 3 in diameter; suture irregular. (Pl. VII, Fig. 9.) United States: Illinois; Indiana; Kentucky; Ohio. Common and gen- erally distributed in April and May. South America, south Chile. 83. ZYGNEMA STERILE Transeau 1934. Trans. Amer. Micros. Soc. 53, p. 212. Vegetative cells 44-54 x 22-69 with heavy cell walls, often with 42 ZYGNEMATACEAE an outer pectic layer 6-15 in thickness; conjugation unknown; repro- duction by akinetes; akinetes heavy-walled, completely filling the cells, brown at maturity, often distinctly colligate. (Pl. VII, Fig. 11.) United States: Prairie regions of Oklahoma; Texas; Wisconsin; Mich- igan; Illinois; Indiana; Ohio. Not uncommon. Greece (Skuja, 1937); Asia Minor (Skuja, 1932). The brown color of the akinetes apparently results from chemical changes in the protoplasts and chromatophores. I have had this alga in cultivation during 2 successive years. It grew well, produced akinetes, which germinated and produced new filaments. During a 5 year period near Columbus, Ohio, it grew abundantly in a pond, but produced no spores, 84. ZYGNEMA QUADRANGULATUM Jao 1940. Sinensia. 11, p. 294, Pl: 4; Fig. 3; Vegetative cells 24-27 x 25-100, with 2 stellate chromatophores; reproduction by aplanospores only; aplanospores cylindric-ovoid, 25-29" x 20-284; median spore wall dark blue, smooth, lamellate. (Pl. VII, Fig. 14.) China, Hunan. 85. ZYGNEMA HYPNosPoRUM Rich 1935. Trans. Roy. Soc. S. Africa. 23, p. 125. Vegetative cells about 33 in diameter, with 2 large stellate chro- matophores; reproduction by aplanospores only; aplanospores cylindric- ovoid, 34 x 34-70; median wall scrobiculate, blue. (Pl. VII, Fig. 12.) Africa, South Rhodesia, July 3, 1930 (Stephens Coll.). 86. ZYGNEMA scHWaBEI Krieger 1941. Zygnemales. Rabenhorst’s Kryptogamenflora. 13, p. 261. Vegetative cells 17-20 x 36-71; reproduction by aplanospores only; spores cylindric filling the cells, 19-21“ x 37-70; median spore wall thick yellow-brown, scrobiculate, pits 1-3 in diameter and 2-64 apart, with several irregular sutures. (Pl. VII, Fig. 10.) South America, southern Chile. 87. ZYGNEMA BORZAE Krieger 1941. Zygnemales. Rabenhorst’s Kryptogamenflora. 13, p. 264. Vegetative cells 24-26 x 18-55; reproduction by aplanospores only; aplanospores cylindric filling the sporangium wall, 14-27" x 18-544; median wall thick, blue, punctate with irregular elongate and variously curved pits 0.5 x 1-2 in size. (Pl. VII, Fig. 4.) Rumania, Transylvanian Alps at 6,000 feet, attached to stones in streams, ZYGNEMA 43 88. ZYGNEMA SUBCYLINDRICUM Krieger 1941. Zygnemales. Raben- horst’s Kryptogamenflora. 13, p. 262. Vegetative cells 28-35 x 54-71; reproduction by aplanospores only; spores cylindric filling the cells, 29-334 x 55-70; median wall brown, granulose and with shallow pits, and 1-2 irregular sutures. eel, VII, Fig. 13.) Germany; Bohemia. This is the Z. cylindricum figured by Czurda. It differs from Z. cylin- dricum Transeau in the granulose markings on the spore wall. 89. ZYGNEMA IRREGULARE Krieger 1941. Zygnemales. Rabenhorst’s Kryptogamenflora. 13, p. 263. Vegetative cells 40-42" x 68-82; reproduction by aplanospores only; spores cylindric-ovoid with very heavy walls; median wall brown, outwardly finely verrucose, with irregularly and widely separated pits 3-6 in diameter and 4-26u apart. (PI. VII, Fig. 8.) Germany, Mark Brandenburg. SPECIES NOT IN PROPER SEQUENCE go. ZYGNEMA MUCIGENUM Randhawa 1938. Proc. Indian Acad. Sci. 8, p. 141, Fig. 25. Vegetative cells 12-14 x 50-100; conjugation both lateral and scalariform; zygospores in one of the gametangia, which is enlarged near the spore; zygospores compressed-globose, 20-224 x 30-364; me- dian spore wall dark blue-green, with scattered punctations; pits 1-1.5 4 in diameter, 3-4 apart. (Pl. XLI, Figs. 6-7.) India, Fyzabad district, December 15, 1937. Should be placed near Number 68. gt. ZYGNEMA GANGETICUM Rao 1937. Jour. Indian Bot. Soc. 16, Pp. 270: Vegetative cells 16-20 x 40-60; conjugation scalariform and lat- eral, zygospores formed in the conjugating tubes and extending into the gametangia; zygospores globose to ovoid, 30-36 x 30-45“; median spore wall yellow-brown and smooth. India, United Provinces, Ganges. Should be near Number 3. g2. ZYGNEMA KWANGTUNGENSE Ley 1944. Simensia. 15, p. 97. Vegetative cells 38-42 x 25-75; conjugation scalariform; recep- tive gametangia slightly inflated; zygospores globose or subglobose, slightly compressed, 44-61 4 x 39-72; outer spore wall smooth, trans- parent; median wall 7-11 thick, lamellate and foveolate; pits very 44 ZYGNEMATACEAE irregular in form and diameter, 1.8-6.5, 1.8-7.2» apart, brown at maturity. (Pl. VII, Fig. 15.) China, rice fields, Tong-Kau, North Kwangtung, March 20, 1942. Should be near Number 61. 93. ZYGNEMA ELLIPSOIDEUM Jao 1947. Bot. Bull. Acad. Sinica. 1, Pp- 97- Vegetative cells 20-22 x 25-40; conjugation unknown; aplan- ospores ellipsoid, with somewhat pointed ends, 15-20 x 22-25(-30) 4; median spore wall yellow-brown, scrobiculate; sporiferous cells cylin- dric, or somewhat inflated on one side. China, Kwangsi, Suijen, May 31, 1938; fairly common in rice fields. This is the first species with ellipsoid spores to be described. Fic. A.—Zygnema ellipsoideum aplanospores and sporangia. Fics. B. and C.— Zygnema mirificum aplanospores, immature and mature. Both figures after Jao. 94. ZYGNEMA MIRIFICUM Jao 1947. Bot. Bull. Acad. Sinica. 1, p. 97. Vegetative cells 15-18 x 25-634; conjugation unknown; outer aplanospore wall similar in shape and just inside the dolioform sporan- gium wall, 22-30» x 30-60 the median wall varies from ellipsoid to ovoid in the bulge of the outer wall, 20-30" x 25-30. The space be- tween the 2 walls is filled with yellowish colloidal material. The median wall is irregularly and minutely scrobiculate, yellow-brown in color. China, Kwangsi, Suijen, June 17, 1938; in rice fields, very common. This is a new type of Zygnema spore, with a colloidal layer between the outer and median walls, and the 2 walls not of the same form. It is probable, however, that the “granulose” surfaces of the median walls of certain other species result from the coagulation of a preceding colloidal layer. g5. ZYGNEMA KHANNAE Skuja 1949. Nova Acta Soc. Sci. Upsali. Ser. 4, 14, p. gg. Pl. 22, Figs. 6-7. Vegetative cells 24-28 » x 30-70", conjugation unknown; reproduc- ZYGNEMA 45 Fics. D and E.—Zygnema khannae aplanospores with outer wall cylindric, and median wall ellipsoid or ovoid. After Skuja. tion by aplanospores, the outer wall of which is cylindric, just inside the sporangium wall, densely punctate; the median wall, formed after con- traction, varies from ellipsoid to ovoid, 22-254 x 25-46, yellow-brown with shallow irregular pits 1.5-5 in diameter. Burma, near Rangoon, 1936. (L. P. Khanna Coll.). List oF THE SpEcIEs OF ZYGNEMA witH NuMBER Papectinainm Vraliscau’ 1934. ... 0.2000. e secant dee eee ne hee ns 13 peeeigrree Vath Gr. Mranseal) LQ2Ai 4222.1.) aise peels ale se Riels oe 15 miracucruicum W =: & G. So West 1897... 8200S soc ee ene nan tenes 67 PTE AIM AUT TSA Ut elutes cyctele giaia oesiah9 5 win ie a testis Serer ee exeneiche taatattes 74 SP ENEECILD MO ZAUCUA NQ322 Se 's.o/. tos oS oie ba ee ieee = cles Pea 62 Ree CS er MOAT gos win ig eseynae sien s 3 gayest syne am aeeeeegt 87 RESPOND JAG LO25 ner, 6 od o't,ao alele wid so 24h ace cones eos 48 BMAP MARCO 2A cis vt uloX A) o's cre cisjuisleis ss ela mele ams shal comets Rees 35 RP RAMEEMIRE IIIT. CIO EQ2Qioxe 5 4 < alstetals «-a)s aisieis a)4)e els iaie = \ Me eine alaialelac dicts 5 gia Chas ES 0 2 eee PPS err ee Ua eae 2 eee ICH UT AmSCAl TOGA isa. ase a - noe de elvan aan ers be mosis 79 Gnayvcospermun FAansgitg TOS...) 2k... SIA Es cna se eae none 68 Raper gene POCA ONG SUS ei soc aidncin se bad yo dees salgemce mn raced 10 PIC OFIORI HE MZULGAVIOI0. 7's 2 << ses aloe sm neler cerns ieee aie 33 Bete rarity AG UEC AT O92 ois orca ich. os ssess% aie apes 2 snide Ostet aheenetS 26 Beat APSAN ETT) IA VEANSCAU TQUA ae atone wie ore as elas 36 enrrane ( Valicher)) A Parad TO24% 422 since ss ca iicins gies weld mines 59 RRL NG ARSEAU LOSA Lhe a Sod Ne feiss lela ye olcta' ee Bigrsintah vv stebeaaTatne ada 6 83 MR LHI OU FATIGCALY TO RAS sii yie yas ors tas) six es sjoipena ere sie shy sive stake 53 PCT ICING ICGICOELUIOAT 4. 30 aise demas disc os ah me sinrcls soaps 88 eet TOV TOA 8 ss25 labialis his nts Witenre eic(ae a Want alia tea yehe eee Dl hae 57 eee! ere eer7o) VEC EO I4 S's a. kia a) AL deel csin ste opts fia wiSim Sipe chelelatees 45 Ber PRUE Z US TOA oa iarc xs inpsilee nin =) shelves ole Polalbiow Slew a Sern naka ees 37 Ree A I Cryo > SHUN As TAG 02.05, ws 2se eins ahals’s screed oie ois 4 Seoleniecw a a Sion 24 PRM APMEROTE ATTN a TOAGY ole teanto di Sa acne alec Babs Goh whS umeera he mene 5, wae 42 Bambi RANG nda TO90. occ 18S wl aitislareereananul bate etaaes acts aioe 25 memosporum. Magnus & Wille 18845). <2. 54555 ose cas bale eases oe 4I Pmrereomraniine (GC. Couch 194452 5 ii. os cos gens nhs ventas 58 Meare ATP EBICIIS: TOGO 58 oc poy sities: «yarawin inate lhc pa. 3) Meteo 52 MP RN SOT AIN TODA 580 205 che oiraa'n Wisin 2 oft Mi bite a sai ncaa ated 49 REREEASEENID. NAOY LOSS 2 i) sis ois a8 cs'o'n olen ss plaunale Ke aia amen s slnnellelelaen 9 RTA OTIS AUN EAC 9 2 os) cues ach in Bpaialbe dave. sida aie’ aloo aus panes 39 ey stage fang . An A de es eee ed Pe Tae ul ee HWA Ler Pe / ; Vi tN AP eg at ian MAb iad eb om, vs Mt ee er ee Bs et ee Ty ent a 7 Bie, i i ye tsncde Ry hci Se CHAPTER THREE THE GENUS ZYGNEMOPSIS (SKUJA) TRANSEAU 1934 The vegetative filaments of the 24 species here classified are usually indistinguishable from those of Zygnema. They may have a thin, or a thick, pectic sheath and they have been found floating in ponds, ditches, and slow flowing streams, not infrequently associated with other species of Zygnemataceae. At the beginning of the reproductive phase, however, they may be distinguished by the partial replacement of the usual cell contents by a transparent refractive gel. Whether the cells become gametangia, or aplanosporangia, some of them lengthen and suc- cessive layers of cellulose are deposited as the protoplast contracts to the middle of the cell. At maturity the zygospores have four, and the aplanospores two, lamellate solid appendages attached to them. As seen in the illustrations, these may be short and stubby, or may be very much longer than the original vegetative cell. All the 19 zygosporic species have isogamous gametes and scalariform conjugation. After the papillae unite in sexual repro- duction the tube is exceedingly narrow, but soon broadens in the plane of the filaments. The zygospore resulting from fusion of the gametes is a compressed, more or less quadrangular pillow- shaped, body which may subsequently become lenticular or irreg- ular in outline. Both the tube development and spore forms resemble those of the quadrangular-spored species of Mougeotia more than those of any species of Zygnema. The outer or first- formed wall bounds the colloidal gel and is composed of cellulose. The median wall is chitinous and in at least one species consists of two layers. Not infrequently yellow or brown granules are deposited between the outer and median walls and may obscure the surface features of the median wall. The innermost wall is transparent and thin and can be seen only when the spore is crushed. Parthenospores are not infrequent in some collections. They have walls similar to those of the zygospores, but are ovoid, smaller, and laterally placed in the gametangia. Aplanospores are common in 5 of the species. They vary in form from ovoid to ellipsoid and have walls similar to those of the zygospores. 49 50 ZYGNEMATACEAE When the zygospores are fully mature, an equatorial suture usually can be seen. In many collections the median wall is con- tracted inwardly and the surface thrown into ridges. The ridges are irregular in position and are not morphological features of the wall. They disappear when the spores are treated with dilute potassium hydroxide, while morphological features of the wall become more distinct. The species of Zygnemopsis may be distinguished readily from those of Zygnema when in a fruiting condition by the cellulose colloid accumulation in the cells, by the initial very narrow con- jugating tubes, and by the round or quadrangular pillow-shaped spores. They differ from the species of Zygogonium in the form of the chromatophores, the absence of cytoplasmic residues in the gametangia and sporiferous cells, in the form of the spores, and in the stages of tube formation. From the species of Debarya they may be distinguished by the Zygnema-like chromatophores; and from Hallasia by the absence of aplanospores from which one, two, or three sporelings develop. Some of the species here classified in the genus Zygnemopsis have been previously placed in the genera: Debarya, Mougeotia, and Zygnema. Key To THE Species oF ZYGNEMOPSIS 1, Reproducing "by aplanospores.4 s.5...5. +05 + ker ass ces eee 12 1. Reproducing by zygospores, sometimes aplanospores also..... 3 2. Diameter vegetative cells mostly less than 8u............ 3 2. Diameter vegetative cells mostly between 8 and 16p...... 4 2. Diameter vegetative cells mostly 16” or more..........-. II 3. Median spore wall punctate, yellow, diameter vegetative cells 4-6p........ 1. Z. sthangensts 3. Median spore wall smooth, golden- brown, diameter vegetative cells 6-72 2. Z. orientalis 3. Median spore wall scrobiculate, yellow, diameter vegetative cells 6-8m........ 4. Z. floridana 4. Shorter axis of zygospores less than 32/..........00+0005 5 4. Shorter axis of zygospores 32 OF MOFe€..........eeeeeees 8 5. Diameter vegetative cells mostly less than 12/.............05 6 5. Diameter vegetative cells mostly more than 12/...........+. 7 6. Median spore wall smooth, choco- late: brow ii) Avs eens venleas 5. Z. minuta ZYGNEMOPSIS 51 6. Median spore wall punctate, yel- Fwy -DEOWilte ol ciuigtts bc oe tae Seger 6. Z. desmidioides 6. Median spore wall punctate, chest- ia (leroy), a el eee AE ee 7. Z.columbiana 6. Median spore wall punctate, yellow 9. Z. tiffaniana 6. Median spore wall scrobiculate, yel- Popmactn Airat Msc Satan Sime 10. Z. sinensis 6. Median spore wall finely scrobic- ulate, yellow-brown .............. 8. Z. americana 7. Median spore wall scrobiculate, yellow, | ECTSHe ae TAR IE Ses Nic 10. Z. sinensis 7. Median spore wall scrobiculate, yellow- BEG PoranUlose:sjc)s ess ck ee tle ses 12. Z. splendens 8. Median spore wall punctate, or Uculanes @ranlose aes ee yaiaials <1: 15. Z. 1yengarit 8. Median spore wall punctate, choc- VENTS 07 (04 CHDLOR OOHEAG Re Ase 17. Z. sphaerospora SeMedian spore wall scrabictlate. .sc/3 22. «sec aee son sene oe 9 g. Zygospores 32-364 x 36-42", golden Welow SUG se wadss Kove su ceases 14. Z. stephenstae g. Zygospores with shorter axis more than 36...............4. 10 10. Median spore wall smooth or undu- late, yellow-brown, granulose..... 11. Z.indica 10. Median spore wall deeply scrobic- ulate, pits 2-4 angular........... 13. Z. wuchangensts 10. Median spore wall scrobiculate, pits BRP LOMRICULS ER ean natn tlds 16. Z. quadrata 11. Zygospores 36-52, brown to green... 18. Z.lamellata 11. Zygospores 24-30 x 30-48, brown... 20. Z. decussata 11. Zygospores 28-36 x 48-60, brown... 21. Z. spiralis 12. Vegetative cell diameter 8u or less 3. Z. gracilis me Viecettive cell diameter FA 22 flat c5)a8, 4 san ewe one