238 AQUATIC PHYCOMYCETES 



rangium and swimming immediately away; resting spore sessile, spher- 

 ical, 25-30 [x in diameter, with a thick brownish wall, outer surface 

 covered with small spines, germination not observed. 



Parasitic on Closterium sp., causing an epidemic in culture dishes, 

 Navicula sp., (?) Sphaeroplea annulina, Cohn (Ioc. cit., pi. 16, figs. 

 10-20), (?) vegetative cells of Oedogonium rivulare, (?) Melosira various, 

 (?) Eunotia amphioxys, Braun (loc. cit.), germlings of O. tumidulum, 

 Kloss (in Braun, 1856b: 587). Closterium lunula, Penium digitus, Pin- 

 nularia viridis, Schroeter(?)(1885: 191), Germany ; Pleurotaenium trabec- 

 ular Closterium sp., Staurastrumsp., Cejp( 1933a: 3, pi. 1, figs. 5-8, pi. 2, 

 fig. 1), Czechoslovakia; Closterium spp., diatoms, Dangeard (1886a: 

 295), France; Penium digitus, Pleurotaenium trabecula, Genicularia sp., 

 Spirotaenia sp., Serbinow (1907: 160, pi. 5, figs. 1-3), Finland; Oedo- 

 gonium sp., Litvinow(1953: 79). Latvia; Spirogyra sp., Atkinson (1894: 

 503; 1909a: 321, figs. 1 a-d), Cladophora glomerata, Karling (1941a: 

 387). Oedogonium sp., Karling (1941b: 108), Spirogyra sp., Karling 

 (1948c: 508), United States; Ulothrix sp., W. R. I. Cook (1932a: 

 136, figs. 13-19), Great Britain; Spirogyra sp., Tokunaga (1934b: 

 390, pi. 11, fig. 5), Japan; Spirogyra sp., Berczi (1940: 81), Hungary; 

 pine pollen, Gaertner (1954b: 21), Egypt, Northwest Africa, West 

 Africa, Equatorial East Africa, South Africa. 



Though spherical sporangia of this species were observed by Braun 

 on several hosts, it was Cohn who reported the nonsexual repro- 

 duction and the branched rhizoids. Braun identified the sporangial 

 part of Conn's fungus with his own, but declared that the rhizoids 

 probably belonged to another organism! Cohn also observed the pene- 

 tration of the germ tube of the zoospore and the formation of the rhi- 

 zoids within the alga. Later, however, he declared the same species 

 on Sphaeroplea to be without rhizoids. 



The species is a difficult one to delimit and, as Fischer (1892: 91) 

 aptly pointed out, is either a widespread omnivorous organism or is 

 a collective species in need of further investigation. No sound limi- 

 tations can be established for it until the morphological variations 

 which occur on dilferent substrata in strains derived from single spores 

 are studied and such studies have not as yet been forthcoming. In 

 the preceding diagnosis an attempt was made to stay within the con- 



