94 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



mentioned fungi. The endophytic mycelium is never- 

 theless irregular, 5-8 ft, with occasional septa (figs. 

 16-20) as in the previous species, but the ectophytic 

 mycelium, 1.5—5 /x in diameter, is highly branched, 

 septate, and bears numerous thin-walled conidia 

 (12-1.5 /x in diameter) in chains on lateral branches 

 (fig. 15). Zoosporangia, zoospores, resting spores, 

 and chlamydospores are unknown. 



Whether or not R. Oedoffonii Skvortzow ('25, 

 p. 432, fig. 14) is a valid lagenidiaceous species is 

 uncertain at present. This species parasitizes Oedo- 

 gonium sp. in North Manchuria and is character- 

 ized by a branched, hyaline, fine, 1-17 /x thick 

 endophytic and a sparse ectophytic mycelium. The 

 resting spores are hyaline, smooth-walled, 11.5- 

 18.5 /x long by 7.4-1 1.1 /x wide, and contain a large 

 refractive globule. Zoosporangia and zoospores have 

 not been observed. 



shaped and laterally biflagellate Achlyogeton might 

 well be merged with Myzocytium provided both 

 genera are also similar in type of sexual reproduc- 

 tion. The presence of posteriorly uniflagellate zoo- 

 spores with a single refractive globule and the lack 

 of antheridia and oogonia at present militate against 

 this view. Achlyogeton is accordingly excluded from 

 the Lagenidiaceae for the time being. It may be noted 

 here that its thallus resembles that of Septolpidium 

 which is likewise characterized by uniflagellate zoo- 

 spores. The latter, however, do not encyst at the 

 mouth of the exit tube as in Achlyogeton but swim 

 away after a brief pause — a characteristic which 

 precludes close relationship with the latter genus, 

 according to Sparrow ('36). Six years later, how- 

 ever, Sparrow ('42) reversed his opinion about this 

 characteristic and included Achlyogeton with Sep- 

 tolpidium and Bicricium in a new family, the Achlyo- 

 getonaceae, of the Chytridiales. 



EXCLUDED GENERA 

 ACHLYOGETON 



Schenk, 1859. Bot. Zeit. 17: 399. 



Thallus intramatrical, usually elongate and sep- 

 tate, consisting of a chain or linear series of fairly 

 short oval, ellipsoidal, egg- and spindle-shaped seg- 

 ments with truncate ends ; constricted at the septa ; 

 rarely dwarfed and unicellular, holocarpic. Spo- 

 rangia of the same size and shape as the thallus 

 segments or unicellular thalli, with one exit tube of 

 variable length which may or may not be inflated 

 before passing through the host wall, extending a 

 short distance beyond surface of host. Zoospores 

 delimited in the sporangium; diplanetic, emerging 

 singly in succession, and encysting in a loose cluster 

 at the mouth of the exit tube as in A My a; emerg- 

 ing from the individual cysts and swimming away ; 

 posteriorly uniflagellate (?) with a small refractive 

 globule. Resting spores (doubtful) formed asexu- 

 ally (?) by the contraction and encystment of the 

 cell content; germination unknown. 



The development and structure of the vegetative 

 thallus are so strikingly similar to Myzocytium that 

 it is very difficult to avoid a suspecion that Schenk 

 may have been incorrect about the number, relative 

 lengths and insertion of the flagella on the zoospores. 

 This possibility is further suggested by the fact that 

 he figured the swarmspores of Myzocytium, Lageni- 

 dium, and Pythium as uniflagellate also. Although 

 Martin and Tokunaga saw encysted zoospores, they 

 unfortunately did not determine the number of 

 flagella and thus settle this important question. It is 

 to be noted in this connection that the zoospores of 

 Lagenidium Oedogonii also may encyst in a cluster 

 at the mouth of the exit tube, which shows that such 

 a character is common to the Lagenidiaceae and is 

 in itself no basis for excluding Achlyogeton from 

 this family. Should the zoospores prove to be bean- 



A. ENTOPHYTUM Schenk, I.e. PI. 13, figs. Al-8. 



Thallus composed of one to 15 segments. Spo- 

 rangia oval, broadly ellipsoidal and egg-shaped 

 with truncate ends, 15.6-33.6 /x X 9.6-20.4 ti; exit 

 tubes 27-60 /x X 3.6 xi. Primary zoospores elongate 

 as they emerge; cysts spherical, 4/x; secondary 

 swarmers more oval, rounded at the anterior and 

 tapering slightly at the posterior end ; flagellum ap- 

 proximately three times the length of the spore. 

 Resting spores hyaline, smooth, oval and spherical. 



Parasitic in Cladophora sp. in Germany (Schenk, 

 I.e.) ; Cladophora sp. and Anguillula sp. in Russia 



plate 24 

 (Fig. 1 after Couch, '41; figs. 2-11 after Dangeard, '91; 

 figs. 12-20 after Fritsch, '03.) 



Fig. 1. Laterally biflagellate isocont zoospore of Resti- 

 cwlaria sp.; anterior flagellum with tinsel; posterior flagel- 

 lum with tail piece. 



R. nodosa 



Fig. 2. Germination of zoospore and infection of Lxjng- 

 bya filament. 



Figs. 3, 4. Later developmental stages of thallus. 



Fig. 5. Coarse irregular branched thallus. 



Fig. (i. Emerged vesicular mass of protoplasm prior to 

 cleavage; encysted zoospore above. 



Fig. 7, 8. Distribution of nuclei in thallus. 



Fig. 9. Plasmogamy of adjacent protoplasts in oospore 

 (zygospore) development. 



Figs. 10, 11. Young and mature oospores (zygospores). 



Fig. 12. Mycelium with internal chlamydospore. 



Fig. 13. Stages in chlamydospore formation. 



Fig. 14. Mature chlamydospores. 



R. boodlei 



Fig. 15. Extramatrical mycelium with spores. 

 Fig. 1G. Young thallus from germinated spore. 

 Figs. 17, 18. Intramatrical mycelium. 

 Fig. 19. Infection of two Tolypothrix filaments. 

 Fig. 20. Thallus with germinated spore and three infec- 

 tion hyphae. 



