936 AQUATIC PHYCOMYCETES 



tubes which may extend considerably beyond the surface of the host 

 filament. Zoospores hyaline with numerous small granules, oval, spher- 

 ical, or somewhat reniform, 2.3-5.7 u. x 2.9-4.3 y., usually about 4.2 x 

 3.1 '{x, with two approximately equal flagella attached laterally near the 

 anterior end. Resting spores sexual and asexual or parthenogenetic, 

 spherical or oval, 22.8-122.4 { x (usually about 50.0 41.0 <x), brown, 

 with several or commonly one, large refringent globule. Endospore 

 composed of cellulose, smooth, 1.0-1.5 p in thickness. Exospore not 

 composed of cellulose, varying from 1 .0-1 1 .4 u. in thickness, with warty 

 protuberances, small or large, narrow or broad-based spines, hair-like 

 fibrillae or with an entire, undulant or slightly serrate margin. Male 

 cells, when present, may or may not discharge contents into female 

 thall'us, similar in appearance to zoosporangia, one to three attached 

 to one female thallus, spherical or oval, thin-walled, smooth, sometimes 

 embedded in the exospore. Resting spore in germination transformed 

 into a sporangium liberating zoospores by means of an exit tube" 



(McLarty, loc. cit.). 



Parasitic in Achlya flageUata, McLarty (loc. cit.), Canada; Achlya 

 flagellata, Karling (1949a: 275), United States; Achlya sp., Das-Gupta 

 and John (1953: 169, figs. 8-12), India. 



Possibly, as McLarty suggests, this fungus is referable to Olpidwpsis 



fusiformis. 



Olpidiopsis index Cornu 



Ann. Sci. Nat. Bot., V, 15: 145, pi. 3, fig. 11. 1872 



Sporangium narrowly ellipsoidal, with a thin smooth colorless wall 



and a single discharge tube; zoospores not observed; resting spore 



spherical, with a somewhat thickened wall densely covered with short 



slender spines; companion cell spherical, sparingly covered with short 



slender spines. 

 Parasitic in Achlya sp. (preparations), France; Saprolegnia, Sorokin 



(1883: 29, fig. 30), Asiatic Russia. 



Differing from Olpidiopsis saprolegniae in the spiny wall of the 

 companion cell and, to a lesser degree, in the more narrowly ellipsoidal 

 sporangium. 



