882 AQUATIC PHYCOMYCETES 



merits of hyphae long, cylindrical, 9 to 12 a in diam., 130 to 200 \i in 

 length; upper segments rather short, 2.5 to 6 a in diam., 40 to 100 u, in 

 length. Hyphal membrane smooth, hyaline. 



"Zoosporangium unknown. 



"Oogonia single, terminal, spherical, 23 to 48 \x in diam., rarely 

 pyriform to broad cylindrical, containing 2 to 12 (usually 4 to 7) oo- 

 spores ; membrane thin, smooth, hyaline. Oospores spherical to subspher- 

 ical, 16 to 24 u in diam., with a large eccentric oil drop; membrane 1.? 

 to 1.8 [jl in thickness, punctated when matured. Antheridia terminal, 

 single on from 2 to 3 segmented filamentous antheridial branches 

 arising from segment just below oogonia; long, cylindrical, curved, 

 containing 4 to 10 antheridial cells. Antheridial cells spherical, hyaline, 

 smooth, 4.4 to 4.9 u, in diam., arranged in a single row" (Indoh, loc . 

 cit.). 



Indoh's observations confirm the fact that the multisporous condition 

 of the oogonium is not due to an extraneous organism. 



In fresh water and soil on flies and hemp seeds used as bait. Hum- 

 phrey (loc. cit.), United States; Indoh {loc. cit.), Japan. 



KEY TO THE GENERA OF THE RHIPIDIACEAE 



Basal cell usually giving rise to hyphal branches bearing the reproduc- 

 tive organs; oospores formed (except in Rhipidium parthenosporum) 

 Basal cell slender, usually poorly defined; sporangia smooth-walled; 



oospore with undulate outer wall Sapromyces, p. 883 



Basal cell usually stout and well defined; sporangia smooth-walled 

 or spiny or both; oospore with reticulate or cellular outer wall 

 Oospore wall cellular; sporangia smooth and spiny-walled 



Araiospora, p. 887 

 Oospore wall reticulate; sporangia smooth-walled Rhipidium, p. 893 

 Basal cell never giving rise to hyphal branches, the reproductive organs 



arising directly from it; parthenospores formed . . . Mindeniella, p. 901 



RHIPIDIACEAE 



Thallus always more or less well differentiated into a basal cell, 

 holdfasts, and jointed hyphal branches on which are borne well-defined 

 pedicellate reproductive organs; zoosporangia smooth- or spiny-walled; 



