300 AQUATIC PHYCOMYCETES 



branched, arising from a main axis, which is occasionally slightly 

 swollen; zoospores spherical, small, 2.5-3.9 \x in diameter, with a 

 delicate fiagellum and a few small colorless globules, escaping upon 

 the deliquescence of the papilla; resting spore extramatrical, irregular 

 in shape, 6-12 \l in diameter, hyaline, smooth, with one to several 

 large refractive globules in the cytoplasm, germination not observed. 



Parasitic on Penium, Cylindrocystis, Phycastrum, palmellaceans, pin- 

 nularians, rotifer eggs, Zopf (loc. cit.), Spirogyra sp., Rieth (1954: 

 171), Germany; rotifer eggs, Scherffel (1904: 116), Hungary; Navic- 

 ula sp., Sparrow (1933c: 519, pi. 49, fig. 13), United States; rotifers 

 and nematodes, Karling (1946b: 2), Brazil. 



On desmids the sporangia were generally grouped at the isthmus 

 of the cell. Rotifer eggs soon died after being attacked and their con- 

 tents, eventually, were nearly completely absorbed by the fungus. 



The species is of interest because of its ability to live on a variety 

 of substrata. Since the sporangium has so distinctive a configuration 

 there is little question but that the same organism is involved in all 

 the instances reported. 



IMPERFECTLY KNOWN SPECIES OF RHIZOPHYDIUM 



SECTION I 



On Fresh-Water Algae 



? Rhizophydium caudatum (Reinsch) de Wildeman 



Bull. Soc. Roy. Bot. Belg. (Mem.), 35: 38. 1896 



Olpidium caudatum Reinsch, J. Linn. Soc. London (Bot.), 15: 215. 1877. 

 Sphaerostylidium caudatum (Reinsch) Berlese and de Toni, in Saccardo, 

 Sylloge fungorum, 7: 309. 1888. 



Like Rhizophydium ampullaceum, but larger (12-13 ^jl in diameter) 

 and with thicker walls. 



On Schizosiphon kerguelenensis, coll. Eaton, Kerguelen Islands. 



