940 AQUATIC PHYCOMYCETES 



observations of Cornu and Sparrow. The latter investigators have found 

 O. inerassata on Achlya. There can be little doubt that Shanor studied 

 his material far more extensively. In view of the host specificity clearly 

 demonstrated by Shanor in his own material and in other species of the 

 genus, it is possible that different physiological strains or even diffeient 

 species are involved. Because of the lack of a specific description by 

 Shanor of his fungus the descriptions of O. major and O. vexans are 

 appended and their names included in the key to the species (below 

 that of O. inerassata). 



Olpidiopsis major Maurizio 



Jahresbericht Naturforsch. Gesell. Graubiindens, Chur, 38: 15, pi. 1, figs. 4-9. 



1895 



Sporangium spherical and 23.5-80 \l in diameter or ovoid and 22-62 

 \l wide by 70-124 y. long, wall smooth, thin, colorless, generally in the 

 swollen apical part of the host hypha, with from one to four (mostly 

 two) narrowly cylindrical discharge tubes of variable length; zoospores 

 ovoid, biflagellate, emerging simultaneously through the discharge 

 tubes; resting spore ellipsoidal, 74.5-105 \x long by 30-50 u. broad, 

 thick-walled, the outer wall light yellow and strongly undulate, germi- 

 nation not observed; companion cells from one to four (mostly two), 

 spherical and 18.5 [i.in diameter or somewhat ellipsoidal and 15.5-21.5 [i 

 wide by 28-31 \x long, wall smooth, thin, colorless. 



Parasitic in Saprolegnia thureti, S. hypogena var. V, Switzerland. 



Placed in synonymy with Olpidiopsis inerassata by Karling (1942e), 

 see remarks under that species, above. 



Olpidiopsis vexans Barrett 



Ann. Bot. London, 26: 231, pi. 23, figs. 15, 19-21, pi. 24, figs. 26-27, 32-39, 

 pi. 25, figs. 40-42, 44, 47-71, pi. 26, fig. 75. 1912 



(Fig. 75 C, p. 939) 



"Sporangia single or multiple, formed in terminal or intercalary 

 swellings of the host hyphae, elliptical, oval, or spherical, very variable 

 in size, up to 176 jj. in diameter, with smooth, colorless membrane, 

 colorless contents, and one to several unbranched exit tubes; zoospores 



