96 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHVCOMYCETES 



(Sorokin, '76, '83, '89); Cladophora sp. in Iowa, 

 U. S. A. (Martin, '27) and Japan (Tokunaga, '31). 

 The thalli which Sorokin ('76) figured in Anguil- 

 lula are somewhat similar to those of Myzocytium, 

 and there is accordingly the possibility that he may 

 have confused this species with M. vermicolum. He 

 is the only one to have reported A. entophytum on 

 hosts outside of Cladophora. He nevertheless re- 

 ported that the zoospores encyst in a cluster at the 

 mouth of the exit tube in the same manner reported 

 by Schenk, although lie did not illustrate them. 



Tokunaga found resting spores accompanied by 

 a small, spherical, hyaline companion cell which he 

 believed may relate to a species of Olpidiopsis para- 

 sitic in Achlyogeton. 



Achlyogeton solatium Cornu ('70), parasitic in 

 Oedogonium obsidionale, is imperfectly known, very 

 doubtful, and has never been figured. Its thallus is 

 filamentous, branched, and apparently extends 

 through several host cells. The sporangia are de- 

 limited at irregular intervals along the thallus and 

 form a single exit tube which is seven to eight times 

 the diameter of the host cell in length. Three to 

 twelve zoospores emerge from the sporangia and 

 encyst in a cluster at the mouth of the exit tube, and 

 after a while they emerge leaving the cysts behind 

 as in Achlya. In addition, Cornu, reported the pres- 

 ence of an extremely irregular, cylindrical oogonium 

 with one to several oospores, but he did not observe 

 the character of the antheridium. Fischer ('92) re- 

 garded Cornu's fungus as a species of Pythium, 

 while Minden disregarded it entirely. 



Achlyogeton rostratum Sorokin ('76) is a doubt- 

 ful species. It parasitizes Anguiliula and consists of 

 chains of short oval segments or sporangia, 5—6 //, X 

 7—9 fj., with one straight, curved, or tortuous exit 

 tube which becomes markedly inflated before pass- 

 ing through the host wall (figs. 11, 12). Zoospores 

 and resting spores are unknown. Inasmuch as Soro- 

 kin did not observe the zoospores and their behavior, 

 the relation of this species to Achlyogeton is ques- 

 tionable. The thalli shown in his figures are funda- 

 mentally similar to those of Myzocytium and may 

 equally well relate to that genus. The inflation of 

 the exit tube is not a distinctive specific character 

 since Schenk has shown that it may occur in A. ento- 

 phytum also. 



Achlyogeton salinum Dangeard ('32) which para- 

 sitizes the marine algae Cladophora laetevirens and 

 C. flavaescens in France is likewise too little known 

 to ascertain its identity and validity as a member of 

 this genus. Dangeard observed only developing and 

 mature thalli, including sporangia and quiescent 

 zoospores ; so that nothing is known about the num- 

 ber, relative lengths, and position of the flagella in 

 this species as well as its method of sexual reproduc- 

 tion. The mature thalli (figs. 13, 14) are strikingly 

 similar to those of A. entophytum which parasitizes 

 a fresh-water species of Cladophora. On the other 

 hand, they are also similar to the thalli of Myzocy- 

 tium and may equally well relate to a species of this 

 genus. 



PROTASCUS 



Dangeard, 1903. C. R. Acad. Sci. Paris 136: 

 628. (Not Protascus Wolk, 1913.) 



(plate 25) 



Thalli intramatrical, single or numerous, elon- 

 gate, cylindrical, unbranched and unconstricted, 

 straight or curved, and septate; segments separat- 

 ing at maturity and with further growth becoming 

 transformed into sporangia and gametangia. Spo- 

 rangia cylindrical, flask-shaped, uteriform, pyri- 

 form, and slightly irregular, usually with a single 

 curved or straight short tapering exit tube which 

 may end almost flush with the surface of the host 

 cell or extend for a short distance beyond. Spores, 

 non-motile, slightly curved and clavate, forcibly 

 ejected from the sporangia; adhering to the host 

 cell for some time after germination. Gametangia 

 occurring among sporangia, unicellular, holocarpic, 

 unequal in size, formed from the same or different 

 thalli; conjugation usually lateral, sometimes sca- 

 lariform or end to end; both gametangia contribut- 

 ing to the formation of the conjugation canal; con- 

 tents of the larger female and smaller male game- 

 tangia often contracting toward the canal before 

 plasmogamy; no differentiation of an egg cell and 

 periplasm ; protoplast of male flowing into the fe- 

 male gametangium and fusing with the ooplasm. 

 Resting spores rarely parthenogenetic, lying free in 

 the female gametangium, spherical and smooth with 

 a fatty granular content which gives it a blackish, 

 opaque appearance ; germination unknown. 



In ignorance of its method of sexual reproduction 

 Dangeard placed this genus among the Hemiascales 

 because of its non-motile spores and the manner in 

 which they are ejected from the sporangium. At the 

 same time he called attention to the similarity of its 

 thallus to those of Myzocytium and Lagenidium. In 

 his opinion Protascus may possibly be a transitional 

 genus between the Phycomycetes and higher Asco- 

 mycetes. Since the discovery of its phycomycetous 

 type of sexual reproduction by Maupas, however, 

 Dangeard's views are no longer tenable. Maupas 

 called the resting spores, zygospores, but pointed out 

 the similarity of their method of formation to that 

 of the oospores of Myzocytium. He regarded Pro- 

 tascus as a possible member of Fischer's Merolpidia- 

 ceae, the direction of growth of which has become 

 distinctly oriented by its elongate host. Maire, on the 

 other hand, assigned it to a position between the 

 Lagenidiaceae and what was formerly known as the 

 Ancylistaceae and proposed a new family, Pro- 

 tascaceae, to include it. Fitzpatrick regarded the 

 resting spore as an oospore but was doubtful about 

 the relationship of Protascus with the Lagenidia- 

 ceae. The lack of zoospores sharply delimits this 

 genus from the Lagenidiaceae as the family is now 

 recognized, and it is accordingly excluded. How- 

 ever, inasmuch as it has often been described in re- 

 lation to Lagenidium, Myzocytium, etc., the author 



