CHAPTER 35. Hydronema Carus, Nova Acta Phys. Med. Acad. Caes. Leop. Carol. Nat. Cur. 11:

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1 CHAPTER 35 Achlya Nees von Esenbeck Nova Acta Phys. Med. Acad. Caes. Leop. Carol. Nat. Cur. 11: Hydronema Carus, Nova Acta Phys. Med. Acad. Caes. Leop. Carol. Nat. Cur. 11: Monoecious or dioecious. Sporangia fusiform, naviculate, cylindrical, or clavate; renewed sympodially or by basipetalous development and cymose branching. Spores mono- or dimorphic; when the latter the two flagella are quickly evanescent; primary spores at discharge encysting and clustering at the exit orifice in a spherical, hollow mass that subsequently may fall away from the sporangium; cysts floating free and then germinating to produce laterally biflagellate, reniform planonts, or remaining in the spherical cluster and then releasing the secondary planonts; in some species, the secondary sporangia discharge the spores in a dictyucoid or thraustothecoid manner, or the spores germinating in situ in an aplanoid fashion. Gemmae present or absent; functioning as sporangia, or oogonia, or producing new hyphae directly upon germination. Oogonia lateral on stalks or various lengths, or terminal, intercalary or sessile; variously shaped, but predominantly spherical or pyriform; sometimes reverting to the production of hyphae, or proliferating. Oogonial wall pitted or unpitted; smooth or ornamented on the outer surface, smooth or irregular on the inner. Oospores centric, subcentric, subeccentric, or eccentric; occasionally aborting; one to many in an oogonium; germinating by producing a mycelium directly or by a germ tube bearing a terminal sporangium. Antheridial branches present or absent, or reduced to a hypogynous cell; when present, diclinous, monoclinous, androgynous, or exigynous. Antheridial cells predominantly tubular or clavate; attached apically, laterally, or in a digitate fashion. Type species: Achlya prolifera Nees von Esenbeck, Nova Acta Phys.-Med. Acad. Caes. Leop. Carol. Nat. Cur., 11: The genus Achlya has a blemished early history. From the figures accompanying the description of Bysus aquatica in Florae Danicae (O. F. Müller, 1782:6, pl. 896) it seems likely that the genus was first known under this binomial. The illustrations of this alga do not show sporangia or oogonia, but the clavate ends depicted on some of the filaments recall one of the stouter Achlyas. In 1819, a representative of the genus was accorded yet another binomial, Vaucheria aquatica, this proposed by Lyngbye. It is not clear whether Agardh (1824) was aware of Nees von Esenbeck s work, for he reduced Byssus aquatica, Vaucheria aquatica, Schrank s (1798) Conferva piscium, and Carus Hydronema to synonymy with Leptomitus clavatus, but made no mention of Achlya. In 1949, Kützing included Hydronema as a synonym of Saprolegnia ferax, but as the organism named by Carus was clearly an Achlya, it is obvious that Kützing s concept of Saprolegnia also included Achlya. 473

2 Various proposals to divide the genus into subgenera or subgroups have appeared in the literature. An early attempt at such a division was that by Schröter (1893), in which two subgenera were recognized, Euachlya (for those species with smooth oogonia), and, for the ornamented Achlya spinosa, Acanthachlya. Coker (1923) separated the genus into four subgenera, Centroachlya (centric oospores), Euachlya (eccentric oospores), Glomeroachlya (branched oogonial stalks), and Thraustoachlya (spore release by some sporangia in a thraustothecoid manner). Centroachlya and Euachlya were further subdivided. Three subgenera, erected on the basis of oospore structure, ere proposed by Johnson (1956b). Two of these, Centroachlya and Subcentrica, certainly must be discarded since it is abundantly clear that centric and subcentric oospores can occur in the same species, and even in individual oogonia. Cejp (1959:127, 163, 176) reduced Coker s and Johnson s subgenera to synonymy with sectional designations Prolifera, Apiculata, and Racemosa that he created. Although he did not recognize subgenera, Dick (1973) carefully bundled the various species of the genus into groups based upon such characters as egg structure, racemose or glomerulate arrangement of oogonia, and the nature of oogonial wall ornamentations. The most extensive infrageneric segregation of the genus Achlya seems to be that adopted in 1954 by Naumov. He divided the genus into four subgenera, Proliferae, Hypogynae, Saprolegniopsis, and Thraustoachlya. The largest subgenus, Saprolegniopsis was further divided into two sections, Spinosae and Leiotheca, with the latter split into two subsections, Polyandrae and Brevipedes. Finally, Naumov segregated the subsection Brevipedes into the divisions De Baryanae and Racemosae. This detailed fracturing seems unnecessarily complicated. None of the infrageneric schemes of classification appears, in retrospect, to offer any proof of natural relationships. This being so, the retention (or introduction) of additional names provides only a convenience, and we see no reason to perpetuate a scheme which has no more value than this. Accordingly, we do not recognize subgeneric groupings. Members of the genus have been used extensively in physiological and biochemical studies (Chapters 16, 19, 20), and in ecological work (Chapters 4, 5). Perhaps the genus is best known for the work which has been done with its dioecious species on the hormonal control of sexual reproduction (Chapter 21). Some taxonomic implications have been extracted from analyses of DNA base composition (Green and Dick, 1972). A few species have been shown (Win-Tin and Dick, 1975) to have gametangial meiosis. The taxonomy of the genus is difficult; representatives of the genus do not always fall into place readily. This has, of course, been recognized for some time, and was first pointed out with specifics by Moreau and Moreau (1935a). Members of the genus producing smooth oogonia with eccentric oospores have long been notoriously difficult, and their identification often doubtful. Evidence from an analysis of several hundred collections of these Achlyas has prompted a severe revision of this section of the genus, much as Seymour (1970) did for the ferax complex of Saprolegnia. 474

3 Ordinarily, recognizing Achlyas in baited cultures or on organic substrates is done with ease, but there are exceptions that are sure to be encountered. A few species A. dubia, for instance practice thraustothecoid and dictyucoid spore discharge particularly from the secondarily produced sporangia. It is essential, therefore, that young cultures be examined so that the nature of discharge of the first-formed sporangia can be determined. Assignment of individuals to the genus is on the basis of these primary sporangia. By the inclusion into Achlya of two species formerly assigned to de Bary s (1888) Aplanes, we have admitted taxa that consistently produce sporangia in such small numbers and so rarely that the species effectively are seen only as asporangiate forms. The two species, A. treleaseana and A. androgyna, are recognized easily by their dolioform, intercalary oogonia (these often develop only after 4 7 days in gross cultures), and appear to be restricted to acid bog habitats. See also, remarks under Protoachlya and Brevilegnia. Key to the species of Achlya 1. Thallus monoecious when isolated, although some cultures capable of cross-conjugating (interspecific mating) Thallus dioecious, being potentially antheridial or oogonial donors, when isolated; but some cultures capable of self-conjugation and expressing it on isolation Oospores centric, subcentric, or both Oospores eccentric Sporangia sparse or abundant, but present in initial growth period of isolates; special culture conditions not required to induce sporangia Sporangia extremely rare, and not present in initial growth period of isolates; may be induced only by special culture conditions Oogonial wall densely ornamented Oogonial wall predominantly smooth, but some oogonia may be very sparsely ornamented Oogonial wall ornamentations mammiform or predominantly so A. radiosa (p. 481) 5. Oogonial wall ornamentations not mammiform or only very rarely and inconspicuously so Antheridial branches lacking A. stellata (p. 484) 6. Antheridial branches present, though sometimes sparse Oogonial wall ornamentations papillate Oogonial wall ornamentations predominantly stout, lobed, truncate, indented, broadly bifurcate, 475

4 or wart-like; occasionally long-conical or long-cylindrical A. spinosa (p. 484) 8. Oogonia positioned in a racemose fashion on short stalks producing closely attending androgynous antheridial branches A. colorata (p. 486) 8. Oogonia positioned at irregular intervals on short or long stalks that are often coiled or twisted; antheridial branches monoclinous or androgynous A. papillosa (p. 489) 9. Antheridial branches strictly diclinous, and often deliquescing Antheridial branches some combination of monoclinous, androgynous, and diclinous, but never strictly the latter; seldom if ever, deliquescing Oospores small, predominantly µm in diameter a. oblongata var. oblongata (p. 490) 10. Oospores large, predominantly µm in diameter A. oblongata var. gigantica (p. 493) 11. Oospores centric A. oligacantha (p. 494) 11. Oospores subcentric, or both subcentric and centric Oospores subcentric Oospores both centric and subcentric Oospores large, predominantly µm in diameter A. megasperma (p. 496) 13. Oospores small, predominant size less than 30 µm in diameter Antheridial branches predominantly diclinous; generally no more than 3 oospores per oogonium a. bonariensis (p. 497) 14. Antheridial branches predominantly androgynous; generally 8 or more oospores per oogonium a. polyandra (p. 498) 15. Oogonia generally positioned in a racemose fashion on the principal hyphae; not apiculate; antheridial branches predominantly androgynous A. racemosa (p. 500) 15. Oogonia not racemosely arranged; frequently or occasionally apiculate; antheridial branches predominantly monoclinous A. apiculata (p. 504) 16. Oogonia predominantly terminal or intercalary; usually dolioform, fusiform, or naviculate; wall pitted, smooth or sparsely to densely papillate; almost always with more than one oospore A. androgyna (p. 507) 16. Oogonia predominantly lateral; usually 476

5 spherical or subspherical; wall unpitted, densely covered with truncate or rounded, conical projections or papillae, and additionally with some cylindrical, straight or hamate, lobed or inconspicuously dented ornamentations; oogonia not predominantly papillate only A. ornata (p. 512) 17. Primary sporangia discharging in a thraustothecoid or achlyoid fashion; secondary ones predominantly in an achlyoid manner a. dubia (p. 513) 17. Primary sporangia discharging only in an achlyoid fashion; secondary ones releasing spores in an achlyoid, dictyucoid, aplanoid, or thraustothecoid manner Large, inflated, subspherical to asymmetrical, thin-walled, unpitted; nonfunctional hyphal swellings intermingled among the oogonia A. diffusa (p. 516) 18. Lateral, inflated, nonfunctional hyphal swellings lacking Oogonia generally lobed, hemispherical, or cylindrical A. intricata (p. 517) 19. Oogonia generally spherical or obpyriform; sometimes angular or subspherical, but not distinctly lobed or hemispherical Oogonia large and inflated, predominant diameter greater than 100 µm A. inflata (p. 518) 20. Oogonia not inflated, the predominant diameter less than 100 µm Oogonial wall predominantly smooth; some oogonia occasionally to rarely provided with one to a few wall projections or having wall substances protruding through some pits, but are neither sparsely nor densely ornamented Oogonial wall crenulate to sparsely or densely ornamented, occasionally to rarely smooth, but predominantly ornamented Antheridial branches seldom or rarely formed, or very sparse but persisting Antheridial branches usually present or frequently formed; persisting or deliquescing after attaching to an oogonium Oospores small, predominantly µm in diameter, almost always single in an oogonium; antheridial branches rarely produced A. oviparvula (p. 519) 23. Oospores predominantly µm in diameter; predominantly 2-4 per oogonium; antheridial 477

6 branches sparse a. caroliniana (p. 520) 24. Oogonia never containing more than one oospore A. pseudoachlyoides (p. 522) 24. Oogonia may contain only one oospore, but some always with more than one Oogonial stalks usually long relative to the oogonial diameter, and generally bent or recurved A. orion (p. 523) 25. Oogonial stalks usually short relative to the oogonial diameter; curved, sinuous, irregular, or straight, but rarely if ever bent or recurved Secondary sporangia frequently discharging spores in a thraustothecoid manner, but some also released in an achlyoid fashion A. irregularis (p. 525) 26. Secondary sporangia not discharging spores in a thraustothecoid manner but may do so in a dictyucoid and aplanoid fashion in addition to achlyoid release Antheridial branches predominantly or nearly exclusively monoclinous or androgynous; when monoclinous, generally of near origin Antheridial branches predominantly or nearly exclusively diclinous, or usually diclinous and monoclinous in various proportions, but monoclinous ones often of distant origin Oospheres often not maturing, or oospores occasionally aborting; oogonial wall smooth; oogonial stalks generally longer than the diameter of the oogonium A. debaryana (p. 527) 28. Oospheres usually maturing, and oospores seldom or rarely aborting; oogonial wall smooth or with sparse projections; oogonial stalks usually as long as the diameter of the oogonium, or shorter Oogonial wall occasionally provided with one to a few cylindrical or conical projections, or wall substances sometimes protruding through pits to give oogonium a sparsely or faintly papillate aspect; oospores predominantly 3-6 per oogonium A. cambrica (p. 535) 29. Oogonial wall smooth; oospores predominantly 6-14 per oogonium A. americana (p. 537) 30. Oogonium predominantly with one oospore A. rodrigueziana (p. 540) 30. Oogonium predominantly with more than 478

7 one oospore Some oogonia provided with one to a few scattered, cylindrical or conical projections, or having wall substances protruding through some pits to give oogonium a sparsely and faintly papillate aspect; predominant number of oospores 3-6 per oogonium A cambrica (p. 535) 31. Oogonia smooth; predominant number of oospores in range of 6-16 per oogonium Antheridial branches strictly diclinous; oospheres predominantly maturing; antheridial branches often deliquescing after contacting oogonia A. prolifera (p. 541) 32. Antheridial branches predominantly but not exclusively diclinous; monoclinous ones often of distant origin; usually not deliquescing after contacting oogonia Antheridial branches occasionally coiling profusely about vegetative hyphae which may or may not bear oogonia, and also coiling around oogonial stalks A. proliferoides (p. 545) 33. Antheridial branches not coiling about vegetative hyphae or oogonial stalks A. debaryana (p. 527) 34. Oogonia never containing more than one oospore A. achlyoides (p. 547) 34. Oogonia may contain only one oospore predominantly, but some always with more than one Antheridial branches lacking or rare to sparse; most oogonia lacking antheridia Antheridial branches present, usually abundant Antheridial branches absent A. abortiva (p. 548) 36. Antheridial branches rarely or sparsely produced, most oogonia lacking antheridia Oogonia predominantly ornamented; smooth ones rarely or seldom produced Oogonia often smooth, but isolates always having some sparsely and unevenly ornamented ones Wall substances occasionally protruding through pits to give oogonia a faint and sparsely papillate appearance; oospores predominantly µm in diameter; antheridial branches generally monoclinous 479

8 and androgynous A. cambrica (p. 535) 38. Wall substance not protruding through pits; oogonia usually with 1-4 oospores; oospores predominantly µm in diameter; antheridial branches generally monoclinous and diclinous A. caroliniana (p. 520) 39. At least some oogonia produced on glomerulate stalks; almost always one oospore per oogonium; oogonial wall generally papillate or tuberculate; oogonia predominantly µm in diameter A. glomerata (p. 549) 39. Glomerulate oogonial stalks absent; predominantly with 1-4 oospores per oogonium; oogonial wall generally crenulate; oogonia predominantly µm in diameter A. crenulata (p. 550) 40. Antheridial cells usually attached to the oogonial wall at short, sometimes inconspicuous, tuberculate projections that are truncate terminally A. subterranea (p. 552) 40. Antheridial cells not attached to tuberculate projections from the oogonial wall Antheridial branches strictly diclinous; oogonial wall ornamentations usually bilobed, cordate, and with intermingled, broad, stout, short tubercles; apex of ornamentations not thin-walled; oospores predominantly 1-2 per oogonium A. lobata (p. 553) 41. Antheridial branches androgynous or monoclinous, never or rarely diclinous; oogonial wall ornamentations usually or predominantly conic-truncate, the apex thin-walled; oospores predominantly 4-8 per oogonium Some secondary sporangia discharging spores in a thraustothecoid manner, others in an achlyoid fashion; oogonial wall provided with stout papillae, rounded or truncate at apex, or with some crenulate protrusions; oogonial stalks not recurved; antheridial branches monoclinous or androgynous A. priomoachlya (p. 554) 42. Secondary sporangia not releasing spores in a thraustothecoid manner; 480

9 oogonial wall provided with stout, conic-truncate projections, but wall not papillate or crenulate; oogonial stalks frequently recurved; antheridial branches androgynous, rarely monoclinous A. recurva (p. 556) 43. Thallus dioecious when isolated, and only some strains capable of self-conjugating, but then not producing androgynous or monoclinous antheridial branches; interthallic mating both antheridial branches and oogonia cross-induced Thallus dioecious or monoecious when isolated, but freely capable of self-conjugation with antheridial branches being monoclinous and androgynous as well as diclinous; in interspecific matings only antheridial branches are cross-induced A. heterosexualis (p. 558) 44. Oospheres predominantly maturing; oospores generally 1-18 per oogonium and predominantly µm in diameter; gemmae cylindrical in both mating strains A. ambisexualis (p. 560) 44. Oospheres infrequently to rarely maturing; oospores generally 5-10 per oogonium and predominantly µm in diameter; gemmae in oogonial thallus spherical to short-cylindrical, spherical to cylindrical in antheridial thallus A. bisexualis (p. 561) Achlya radiosa Maurizio Mitt. Deutsch. Fischerei-Vereins 7:57, figs. 18, (Figure 61 G-M) Achlya decorata Petersen, Bot. Tidsskr., 29: 383, fig. 3a, e (Also in Ann. Mycol., 8: 522, fig. 3a, e ) Achlya asterophora Minden, Kryptogamenfl. Mark Brandenburg, 5:549, fig. 2c Achlya turfosa Johannes, Archiv- Mikrobiol., 14: 599, fig Achlya pseudoradiosa Rogers and Beneke, Rickia, 1: 246, pl Achlya echinulata Beroqui, in, Beroqui de Martinez, Darwiniana, 15:12, text fig. 1A, B; pl. 1, figs. C-E Monoecious. Mycelium moderately to noticeably dense, or diffuse and extensive; hyphae slender, abundantly to sparingly branched. Sporangia fusiform to cylindrical; straight, curved, or irregular; renewed sympodially; x 7-70 µm. Spores 481

10 monomorphic; discharge and behavior achlyoid; in some instances not formed, and sporangium discharging its amorphous protoplasm; primary spore cysts 8-13 µm in diameter. Gemmae lacking. Oogonia lateral, usually in a racemose arrangement, occasionally terminal or intercalary; spherical, subspherical, or broadly obpyriform; (23-) 42-59(-77) µm in diameter, including wall ornamentations. Oogonial wall unpitted; provided generally with mammiform ornamentations, occasionally and additionally with bifurcate ones, infrequently having simple papillae, rarely crenulate; size and density of ornamentations variable. Oogonial stalks (1/4-) l (-5) times the diameter of the oogonium in length; straight, curved, bent, sometimes irregular. Oospores subcentric; spherical, ellipsoidal, or oval; 1-3(-6) per oogonium, and sometimes filling it; (19-) (-41) µm in diameter; germination not observed. Antheridial branches predominantly androgynous, infrequently (?) monoclinous and of distant origin, rarely diclinous; slender, irregular, curved, bent, or twisted; unbranched or once-branched; persisting. Antheridial cells simple; clavate; persisting; apically appressed; fertilization tubes present or absent, not persisting. There should be no difficulty in recognizing this well-marked species (although the list of synonyms suggests otherwise). The oogonial wall ornamentations are predominantly mammiform (Fig. 61J) and even in the rare instances when oogonia are papillate, crenulate, or sparsely ornamented, or generally have long, prominent ornamentations, some projections are always of this distinctive shape (Fig. 61 H, I, L, M). Characteristics other than the nature of the oogonial wall projections ordinarily are not needed for the identification of Maurizio s species. Oogonia of Achlya radiosa usually are accompanied by short, curved, androgynous antheridial branches (Fig. 61 G, J), just as in A. racemosa and A. colorata. The nature of the oogonial wall readily separates these three species. We have never seen monoclinous antheridial branches in the specimens we have examined; they were evidently present (to what degree is not known) in Beroqui de Martinez s (loc. cit.) variant. The synonymy recorded by T. W. Johnson (1956b:43) need not be further justified but there are additional species to consider. Achlya pseudoradiosa clearly is a variant of A. radiosa, as T. W. Johnson et al. (1975) demonstrated. Beroqui s Achlya echinulata digresses from A. radiosa primarily in two characteristics. The Argentinian specimen had somewhat larger oogonia than A. radiosa, and some antheridial filaments (chiefly the monoclinous ones) were longer and more branched than is ordinarily encountered in Maurizio s species. These are but minor digressions of no taxonomic consequence when it is recognized that the oogonia of A. echinulata have mammiform ornamentations and contain a single oospore for the most part. The illustrations provided by Beroqui de Martinez leave no doubt that she had collected A. radiosa. It has been demonstrated by some rather unrefined experimental work by T. W. Johnson et al. (1975) that conditions of culture incubation influence the expression of some structural features of Achlya radiosa. For example, the density of wall 482

11 ornamentation on the oogonia of some isolates was influenced by temperature (and to some degree the source of water used in hempseed cultures): there were fewer wall projections on oogonia of colonies grown at 25 o C in pond water than at 18 o C. Colonies grown in soil extract had slightly larger oogonia than did controls (in charcoal-filtered, distilled water). Oogonia in one test isolate grown in sterile or nonsterile soil extract at 18 o or at 25 o C were sparsely ornamented with large projections. While Johnson and his collaborators found that all isolates grew on semisolid media, they generally did not develop beyond forming oogonial initials. In some instances, where a high nitrogen to low carbon ratio was built into the medium, oospores developed, but only scantily. In sum, while culture conditions modified size, density, and to some extent shape of the oogonial wall ornamentations in forms of A. radiosa, the characteristic mammiform projections were not eliminated. Neither oospore size nor number was influenced by the varied conditions under which the specimens were grown. Gepp (1899) misidentified specimens of Achlya radiosa as A. spinosa. As a consequence of that error, he inferred that his specimens provided a link between debary s A. spinosa and A. stellata. The very characteristic wall ornamentations of A. radiosa do not support Gepp s views. Tiesenhausen (1912) reported two forms of A. radiosa from Switzerland. Only one of those described is recognizable as this species. The only records of the collection of Achlya radiosa in the New World are those from South America and additionally a report of the species from the United States (see distributional records to follow). The species is common in bog and acid lake habitats in Norway and Sweden, particularly in shallow waters containing detritus of Sphagnum spp. CONFIRMED RECORDS: -- BRITISH ISLES: Dick (1969b: pl. 1, figs. 5-7; site of collection not recorded); Forbes (1935a:230, pl. 8, fig. 2); Gepp (1899:200, pl. 400, figs. 12, 13). CZECHOSLOVAKIA: Cejp (1934:191, pl. 1, figs. 14, 15; pl. 3, figs. 1, 2; 1959a:164, figs. 50, 51). DENMARK: Petersen (loc. cit.). GERMANY: Johannes (loc. cit.); Richter (1937:246, fig. 7). ICELAND: T.W. Johnson et al. (1975:115, 117, figs. 1-17). SOUTH AMERICA: Beneke and Rogers (1962:187) first report of A. pseudoradiosa, as an undetermined species; 1970:57; Beroqui de Martinez (loc. cit.); Milanez (1969:43); A. L. Rogers and Beneke (loc. cit.); A. L. Rogers et al. (1970: 101). SWITZERLAND: Maurizio (loc. cit.); Tiesenhausen (1912:283 et sqq., figs UNITED STATES: R. L. Butler (1975): figs ). RECORDED COLLECTIONS: -- BRITISH ISLES: Apinis (1964); Cook and Forbes (1933); Cook and Morgan (1934); Dick (1962, 1963, 1966); Dick and Newby (1961); Forbes (1935b); Hunter (1975); O Sullivan (1965); Perrott (1959, 1960); Pickering et al. (1979); R. E. Roberts (1963); Willoughby (1965, 1974); Willoughby and Collins (1966). DENMARK: A. Lund (1934, 1978); Obel (1910b). GERMANY: Bock (1956). ICELAND: Howard et al. (1970). JAPAN: Hoshina et al. (1958). NETHERLANDS: Beverwijk (1948). SPECIMENS EXAMINED: -- AUSTRALIA (2), RLS. ICELAND (5), NORWAY (8), SWEDEN (10); TWJ: UNITED STATES (3), RLS. Centraalbureau (1). 483

12 Achlya stellata de Bary Bot. Zeitung (Berlin) 46:648, pl. 10, figs. 10, (Figure 65 A-G) Monoecious. Mycelium diffuse, moderately extensive; hyphae slender, sometimes sinuous; sparingly branched. Sporangia sparse or moderately abundant; fusiform, naviculate, or cylindrical; usually slightly irregular; unbranched; wall not thickened in vicinity of exit pore; renewed sympodially; x µm. Spores monomorphic; discharge and behavior achlyoid, very rarely aplanoid; spore cluster not persisting at exit orifice; primary spore cysts µm in diameter. Gemmae lacking. Oogonia terminal or lateral, occasionally to infrequently intercalary; spherical, subspherical, obpyriform, or ovoid, occasionally broadly dolioform to nearly cylindrical, often with a prominent neck; (20-) (-138) µm in diameter, including wall ornamentations. Oogonial wall unpitted; densely ornamented with short or long papillae, or with long, conical, straight or curved projections, apical one occasionally attenuated. Oogonial stalks ( 1 / 3 -) / 2 (-3) times the diameter of the oogonium in length; slender, curved and usually irregular; unbranched. Oospores subcentric; subspherical, oval, broadly ellipsoidal, or irregular or slightly constricted; 1(-8) per oogonium, and usually filling it; (16-) (-48) µm in diameter; germination not observed. Antheridial apparatus lacking. Achlya stellata is discussed in relation to A. spinosa and A. ornata in the respective accounts of these species. The variety multispora of A. stellata described by J. N Rai and Misra (1977a, b) is A. W. Ziegler s (1958a) A. mucronata, which we are assigning to Protoachlya because of its spore behavior pattern. Humphrey (1893) and Coker (1923) believed that Achlya stellata was synonymous with A. cornuta (see excluded taxa). Both A. Fischer (1892: 356) and Minden (1912: 552) provided descriptions of A. stellata though neither evidently saw specimens. Their compilations seem to characterize A. spinosa rather than A. stellata. CONFIRMED RECORDS: -- BRITISH ISLES: Dick (1960b:480, pl. 12, figs. 4-6; text figs. 2, 4a-e, j). GERMANY: de Bary (loc. cit.). ICELAND: T. W. Johnson (1974b:13, figs ); T.W. Johnson et al. (1975:113, figs ). INDIA: G. C. Srivastava (1975a:139). LATVIA: Apinis (1929a:228, pl. 4, fig. 1). MIDDLE EUROPE: Migula (1903:71). USSR: Naumov (1954:70). RECORDED COLLECTIONS: -- BRITISH ISLES: Dick (1963, 1966); Dick and Newby (1961); Ramsbottom (1915a; as A. cornuta)(?). SPECIMENS EXAMINED: -- AUSTRALIA (1), RLS. ICELAND (1), TWJ. Achlya spinosa de Bary Abh. Senckenberg Naturf. Ges. 12:278 et sqq., pl. 4, figs (Figure 65 H-P) 484

13 Monoecious. Mycelium extensive, dense; hyphae slender, moderately branched. Sporangia infrequent; cylindrical, long-clavate, or long-fusiform; slightly irregular and curved; some provided with one or more slender, lateral exit tubes in addition to the terminal exit pore; wall thickened in vicinity of exit orifice; renewed sympodially or in basipetalous succession; x µm. Spores monomorphic; discharge and behavior achlyoid, occasionally dictyucoid or aplanoid; spore cluster not persisting at exit pore; primary spore cysts 8-12 µm in diameter. Gemmae abundant; cylindrical, long-obpyriform, short-clavate; often curved; terminal and intercalary, single and catenulate. Oogonia infrequent; terminal or intercalary, infrequently lateral; spherical, ovoid, or dolioform; (30-) (-108) µm in diameter, including wall ornamentations. Oogonial wall unpitted; densely or sparsely provided with stout, lobed, wart-like, or conical papillae, infrequently also having long, curved or straight, cylindro-conic projections; apical ornamentation occasionally attenuated and straight or irregular; larger projections truncate, indented, or broadly bifurcate. Oogonial stalks short or long, irregular or twisted; unbranched, or with one or two short, lateral, cylindrical projections. Oospores subcentric; ovoid, ellipsoidal, or subspherical, and sometimes laterally compressed or slightly irregular; 1(-4) per oogonium, and usually nearly filling it; (l7-) (-45) µm in diameter; germination not observed. Antheridial branches present, but usually sparse or infrequent; androgynous or monoclinous: short, irregular, slender; unbranched; persisting. Antheridial cells simple; clavate to short-cylindrical; persisting; laterally appressed; sometimes hypogynous but producing a short, lateral, bent branch the apex of which contacts the oogonium; fertilization tubes present or absent. Achlya spinosa and A. stellata seem very closely allied structurally, and are therefore best treated in a single discussion. Both species were relegated to the category of taxa of doubtful affinities by T. W. Johnson (1956b), but Dick (1960b) collected and studied living specimens of the two and correctly considered them to be recognizable entities. We have examined, as had Dick (1960), de Bary s specimens of the two species (British Museum, Natural History), and are satisfied that A. spinosa and A. stellata are reflected as quite different species in the de Bary collection (Figs. 65 F, G and 65 H-M). The cultured specimens we have examined of both taxa conform quite comfortably to the fungi de Bary described. Achlya spinosa and A. stellata have ornamented oogonia, generally produce a single, subcentric oospore in each, and have much the same sporangial configuration (contrary to Dick, 1960b). The differences between the two species, however, are conspicuous. In A. spinosa, the wall projections are stout, prominent, and often irregular (lobed, truncate, bifurcate -- Fig. 65 O, P), while those of A. stellata are more regularly papillate to conical (Fig. 65 A, D, E). The oogonia preserved in the de Bary specimens reflect this difference precisely (compare Fig. 65 H-M and F, G). In contrast to A. spinosa, A. stellata lacks both gemmae and antheridial branches. The type of oogonium wall ornamentations produced by Achlya stellata (papillate or conical, not lobed, truncate, or furcate) evidently is a reasonably stable configuration. 485

14 Two isolates of A. stellata were grown (T. W. Johnson et al., 1975) in several different culture conditions (various combinations of water source and temperature) and the nature of the ornamentations described. In colonies grown in soil extract at 18 o and 25 o C, for example, the wall projections produced by the oogonia were sparse but very much enlarged (T. W. Johnson et al. 1975: figs ), yet retained the configuration associated with the species: elongate-papillate or conical, and broad or slender and nearly echinulate. None was lobed, bifurcate, or irregular as is characteristic of A. spinosa. Modifications in the culture environment changed oogonial size and shape to some extent in A. stellata, but did not influence oospore number or size. Neither gemmae nor antheridia were induced to form. The specimens of Achlya spinosa reported and described briefly by Gepp (1899) were misidentified; they were without question A. radiosa. Minden s A. stellata also was incorrectly named. We believe, as did Dick (1960b), that Minden s plant was A. spinosa. The sparsely developed specimen that Humphrey (1893) described as Archer s A. cornuta was in all probability A. stellata. Archer s fungus, being parasitized, is excluded as a named species of Achlya. CONFIRMED RECORDS: -- BRITISH ISLES: Dick (1960b:43, pl. 12, figs. 1-3; text figs. 1, 3, 4f-i. The legend to text figure 4 is in error; A. spinosa is represented in fig. 4f-i, 4 not 4i). GERMANY: de Bary (loc. cit.; 1888:647). MIDDLE EUROPE: Migula (1903:70). RECORDED COLLECTIONS: -- BRITISH ISLES: Apinis (1958, 1960, 1964); Dick (1963, 1966); Dick and Newby (1961); O Sullivan (1965). FINLAND: Häyrén ( , 1956). GERMANY: Höhnk (1956a). USSR: Logvinenko and Meshcheryakova (1971). SPECIMENS EXAMINED: -- Preserved specimen, de Bary collection, British Museum (Natural History). SWEDEN (1), TWJ. Centraalbureau (1), MWD (1); no oogonia were produced by these cultures. Achlya colorata Pringsheim Sitzungsber. Deutsch. Akad. Wiss. Berlin, Math.-Naturwiss. Kl. 1882:855, 889, pl. 14, figs. 15, (Figure 63 A-C) Achlya racemosa var. stelligera Cornu, Ann. Sci. Nat. Bot. (5 e sér.), 15: Achlya racemosa var. spinosa Cornu, ibid., p Achlya racemosa forma stelligera Petersen, Bot. Tidsskr., 29:383, fig. 3d (Also in Ann. Mycol., 8: 522, fig. 3d ) Achlya racemosa forma pringsheimii Minden, Kryptogamenfl. Mark Brandenburg, 5: Achlya racemosa var. stelligera Minden non Cornu, ibid., p Achlya racemosa forma stelligera Minden, ibid., p Achlya racemosa var. stelligera forma polyspora Shkorbatov, Bot. Mater. Inst. Sporov. Rast. Glavn. Bot. Sada RSFSR, 2: Achlya racemosa forma pringsheimii Milovtsova, Trudy Inst. Bot. Kharkivs kiĭ 486

15 Derzhavniĭ Univ., 1:34, pl. 4, fig Monoecious. Mycelium limited or moderately extensive, dense near substratum; hyphae slender, moderately branched near apices, sparingly branched elsewhere. Sporangia cylindrical, clavate, fusiform, or naviculate; straight, curved, or slightly irregular; renewed sympodially or cymosely, occasionally in a basipetalous fashion; x µm. Spores monomorphic; discharge and behavior achlyoid, rarely dictyucoid or aplanoid; primary spore cysts 9-12 µm in diameter. Gemmae abundantcylindrical, or cylindrical and slightly irregular to obpyriform; terminal or intercalary, single or catenulate. Oogonia lateral, arranged in a racemose fashion, or occasionally terminal; spherical or obpyriform, rarely oval or obovate; (30-) (-115) µm in diameter; inclusive of wall ornamentations. Oogonial wall pitted under area of attachment of antheridial cells, rarely elsewhere as well; sparsely or densely papillate or crenulate, very rarely smooth, rarely with one to a few spines; inner surface smooth or irregular. Oogonial stalks < ½ - 1 ½ (-5) times the diameter of the oogonium, in length; stout, straight or curved, often slightly irregular, unbranched or very rarely branched. Oospores occasionally not maturing; when mature, centric, spherical, or ellipsoidal; (1-) 2-8 (-24) per oogonium, and usually filling it or nearly so; (15-) (-48) µm in diameter; at germination forming a short, unbranched germ hypha bearing a terminal, fusiform, or naviculate sporangium. Antheridial branches androgynous, very rarely exigynous; short and unbranched, or long and branched; 1-7 or more per oogonium, but usually one or two; slender, bent or curved, and often slightly irregular; persisting. Antheridial cells simple; clavate or cylindrical, usually strongly bent; persisting; apically appressed; fertilization tubes very rarely observed. Achlya colorata has had a troubled history largely because of Pringsheim s ( ) evident dissatisfaction with the names (and concepts) of Cornu s A. racemosa var. stelligera and the variety spinosa. Pringsheim proposed the name colorata for Cornu s plants, but inexplicably continued to refer to them as racemosa. In 1882(a) Pringsheim equated A. lignicola with A. colorata. No formal description of A. colorata emerged from Pringsheim s juggling of the nomenclature; hence the first unequivocal reference to the species is limited to certain figures in his 1882(a) paper on sexual reproduction in Achlya and Saprolegnia. The varieties and forms of A. racemosa named by von Minden added nothing to an understanding of A. colorata. Finding both smooth and ornamented racemosely arranged oogonia on the hyphae of a watermold, A. Fischer (1892) concluded that A. racemosa and A. colorata were a single entity. Achlya colorata and A. racemosa do occasionally appear together on the same bait in gross culture, and could easily be taken as a single fungus. To the lengthy synonymy recorded by T. W. Johnson (1956b) for Achlya colorata we add the name A. racemosa forma pringsheimii, described in 1935(a) by Milovtsova. This form is identical with the A. racemosa forma pringsheimii of Minden (loc. cit.), and the one accompanying figure in Milovtsova s account depicts the sexual apparatus of A. colorata. 487

16 The papillate ornamentations on the oogonia of Achlya colorata coupled with the androgynous antheridial branches and short stalks (Fig. 63 B, C) constitute the chief identifying characters of the species. Although it has been shown that the pattern of wall ornamentation in Achlya colorata is influenced by temperature, the characteristic still is reliable taxonomically. Reischer (1949c) demonstrated that as the temperature of incubation increased (cultures grown both on agar and in broth), the abundance and prominence of oogonial papillation decreased. At 25 o C, for example, roughened or smooth oogonia were produced, but only papillate ones developed in cultures incubated at 15 o C. In every broth culture of A. colorata, however, only rarely were there completely smooth oogonia (Reischer, 1949c). Temperature (and perhaps also the physical nature of the medium) influences the degree of wall ornamentations in this species, but not their presence or absence. Working with Achlya racemosa var. stelligera (=colorata) Moreau and Moreau (1935c) found that antheridial branches could convert functionally into vegetative hyphae or oogonia, and the latter into antheridial filaments. In 1927 P. M. Patterson demonstrated that fertilization occurred in A. colorata. This is the only species of watermold alleged to have bacterial galls in contaminated cultures (Moreau, 1946). CONFIRMED RECORDS: -- BRITISH ISLES: E. M. Brown (1938:166); Gepp (1899: pl. 400, fig. 11). CANADA: C. L. Moore ( :229, fig. 15). CZECHOSLOVAKIA: Cejp (1959a:178, figs. 59, 60). DENMARK: Petersen (loc. cit.). FRANCE: Cornu (loc. cit.); Moreau and Moreau (1938:233, pl. 3; pl. 6, figs. 10, 11; pls. 7-9, 11-19, 21, 24; fig. 1). GERMANY: Bock (1956:34, pl. 1); Minden (loc. cit.); Pringsheim (loc. cit; : pls. 21; 22, figs. 1-3); Richter (1937:245). ICELAND: T. W. Johnson (1974b:7, figs ). POLAND: Szwanke (1938:10, pl. 4, figs. 3, 4); Zaborowska (1965:43, fig. 6). RUMANIA: Moruzi and Toma (1968: pl. 2, figs ; pl. 5, figs. 33, 34; fig. 13 on pl. 2 illustrates smooth oogonia; hence may not be this species). UNITED STATES: Beneke (1948b:61); Bretsynder (1943:12); Coker (1923:108, pl, 32); Humphrey (1893:123, pl. 19, figs ); T. W. Johnson (1956a:187; 1956b:23, pl. 2, figs. E-I); P. M. Patterson (1927: p1s. 8-10); Reischer (1949c: figs. 1-6); A. W. Ziegler (1948b:21, pl. 3, figs. 3-8; pl. 4, fig. 1; 1952: 10, pl. 4, fig. 10). USSR: Milovtsova (loc. cit.); Naumova (1955: 134, fig. 1); Shkorbatov (loc. cit.; 1927: 82). RECORDED COLLECTIONS: -- BRITISH ISLES: Apinis (1960, 1964); Cook and Forbes (1933); Dick (1962, 1963); Dick and Newby (1961); Forbes (1935a, (1965); Perrott (1960); R. E. Roberts (1963); Sparrow (1936); Willoughby (1962, 1974); Willoughby and Collins (1966). CANADA: Dick (1971c). DENMARK: A. Lund (1934). GERMANY: Höhnk (1935a, 1956a). INDIA: Dayal and Thakur Ji (1965, 1966); Thakur Ji (1967; 1970: 183, figs ; doubtful -- description and illustrations suggest A. racemosa). LATVIA: Apinis (1929a). NETHERLANDS: Beverwijk (1948). POLAND: Zebrowska (1976a). RUMANIA: Toma (1969, 1971). UNITED STATES: Clausz (1970, 1974); Coker (1927); Coker and Braxton (1926); Höhnk (1933); G.C. Hughes (1959, 1962); C. E. Miller (1965); Scott (1960b); Scott et al. (1963); Slifkin (1964, 1967a); Sparrow (1952b); 488

17 TeStrake (1958); M. W. Ward (1939); A. W. Ziegler (1958b). USSR: Logvinenko and Meshcheryakova (1971). SPECIMENS EXAMINED: -- ICELAND (14), NORWAY (4), TWJ. OCEANIA (2), RLS. UNITED STATES (5), TWJ, RLS. MWD (1). Achlya papillosa Humphrey Trans. Amer. Phil. Soc. (N.S.) 17:125, pl. 15, fig. 28; pl. 20, figs (Figure 62 B-G) Achlya spiracaulis Johnson, Mycologia 41:678, figs. 1, Monoecious. Mycelium extensive, diffuse; hyphae stout or slender, sparingly or moderately branched. Sporangia variable in abundance, often produced only at temperatures below 25 o C; fusiform, naviculate, cylindrical, or clavate; straight or curved; renewed sympodially or in basipetalous succession; x µm. Spores monomorphic, discharge and behavior achlyoid, rarely dictyucoid or aplanoid; primary spores 9-14 µm in diameter. Gemmae, when present, clavate, cylindrical, fusiform, naviculate, globose, subglobose, or obpyriform; occasionally with short, lateral protrusions distally; terminal or intercalary, single or catenulate; usually not disarticulating. Oogonia lateral or terminal, rarely intercalary; obovate, obpyriform, ovoid, spherical, or subspherical, infrequently asymmetrical, naviculate, cylindrical, clavate, obclavate, dolioform, or fusiform; (20-) (-143) µm in diameter, nonspherical ones reaching 193 x 90 µm. Oogonial wall unpitted or pitted under region of attachment of the antheridial cells; densely or sparingly ornamented with short, broad papillae, occasionally with scattered, cylindrical to narrowly-conical protrusions; occasionally to rarely tuberculate. Oogonial stalks 1-12 times the diameter of the oogonium, in length; straight, bent, curved, recurved, loosely or tightly coiled, and usually noticeably irregular in outline; unbranched, occasionally to infrequently oncebranched or with one to several short, lateral, cylindrical evaginations. Oospores centric; spherical or sometimes compressed from mutual pressure; (1-) 4-12 (-44) per oogonium, and filling it or not; (11-) (-46) µm in diameter; at germination forming a slender, short, sparingly branched germ hypha bearing a small, terminal, clavate or fusiform sporangium. Antheridial branches, when present, androgynous or monoclinous, rarely or never diclinous; stout or slender, usually irregular; unbranched or branched; persisting. Antheridial cells, when produced, simple, cylindro-clavate, and slightly irregular; persisting, laterally or apically appressed; fertilization tubes present or absent, not persisting. Achlya papillosa is closely allied structurally to A. oligacantha, and to no other species of Achlya having centric or subcentric oospores. The characteristics that separate these two species are treated in the account of A. oligacantha. In our experience, A. papillosa rarely is found in the New World, but is relatively more common in the Old 489

18 World. It is very prevalent in Iceland soils and waters, and we find it commonly, as well, in the southern Scandinavian Peninsula. Recognizing the structural proximity of Achlya spiracaulis T. W. Johnson, loc. cit.) to Humphrey s A. papillosa, T. W. Johnson and Seymour (1974b) studied variation in nine isolates initially identified with one or the other of these two species. Each fungus was characterized in 17 parameters that, for the most part, were the same as those used by Dick (1969a) in his analysis of Scoliolegnia species. Six of the nine isolates subsequently were selected for further observation. These were propagated in a variety of culture conditions, and eight of the features most essential for the identification of the two taxa then were described for each colony. Incubation temperature and the source of culture water were the two variables. The degree and frequency of oogonial stalk coiling, and the abundance and prominence of oogonial wall ornamentations proved to be sensitive to culture conditions. Since it was precisely on these two features - of proven instability - that A. spiracaulis and A. papillosa had been separated, the two were necessarily merged (T. W. Johnson and Seymour, 1974b). The identification of Achlya papillosa collected in Poland by Stpiczyńska (1962) is probably incorrect, and the author herself seems to have been in doubt on this point. The configuration of the oogonia in her material was that of A. treleaseana (= androgyna), but in antheridial branch origin and the size of the oogonia and oospores, her specimens seem to have allied with A. papillosa or A. treleaseana, Stpiczynśka found only dictyucoid sporangia in the Polish material. The Achlya treleaseana recovered by Muhsin (1977) in Iraq was not that species, but rather A. papillosa. A specimen of A. papillosa generally having long, cylindrical oogonial wall ornamentations (in contrast to the papillate ones ordinarily encountered in Humphrey s species) was reported by T. W. Johnson in 1956(a). CONFIRMED RECORDS: -- AFRICA: Alabi (1967: pl. 12, fig. 3). ICELAND: Howard et al. (1970:67, figs ); T. W. Johnson and Seymour (1974b:446, pl. 1). IRAQ: Muhsin (1977:56, figs. A-E). JAPAN: S. Ito (1936: fig. 34.5); Nagai (1931:15, pl. 3, figs ). SOUTH AMERICA: T. W. Johnson (1956b:29, pl. 3, figs. A, B). UNITED STATES: R. L. Butler (1975: figs ); Humphrey (loc. cit.); T. W. Johnson (loc. cit.; 1956a:187, figs. 8, 9; see also entry for South America). RECORDED COLLECTIONS: -- AFRICA: Alabi (1971b, 1973); Fajola et al. (1979). CANADA: Dick (1971c). GERMANY: Höhnk (1935a). ICELAND: T. W. Johnson (1968). JAPAN: Suzuki (1961f). POLAND: Stpiczyńska (1962: 106, fig. 8)(?). WEST INDIES: Sörgel (1941). SPECIMENS EXAMINED: -- ICELAND (12), TWJ. MWD (1). Achlya oblongata var. oblongata debary Bot. Zeitung (Berlin) 46:646, pl. 10, figs (Figures 60 I-L- 61 A, B) 490