942 AQUATIC PHYCOMYCETES 



Listed as a synonym of Olpidiopsis aphanomycis by Karling (1942e). 



Olpidiopsis aphanomycis Cornu 



Ann. Sci. Nat. Bot., V, 15: 148, pi. 4, figs. 5-11. 1872 



Pseudolpidium aphanomycis (Cornu) Fischer, Rabenhorst. Kryptogamen-Fl., 

 1(4): 37. 1892. 



Sporangia spherical, solitary or in groups of three or more in terminal 

 or intercalary swellings of the host hypha, with a single fairly broad 

 discharge tube; zoospores and resting spore not observed. 



Parasitic in Aphanomyces sp., France. 



Fungi with various types of resting spores have been assigned by 

 later investigators to Olpidiopsis aphanomycis. Dangeard (1890-9 lb: 90, 

 pi. 4, figs. 9-11) figured a spiny spore without a companion cell in 

 Pythium and Aphanomyces, as did Butler also, in the latter genus. 

 Petersen (1910: 539, fig. 27) showed one in Aphanomyces with a warty 

 surface (like that in O. vexans) and bearing a companion cell. What 

 kind of resting spore occurred in Cornu's species is, of course, not 

 known. Of the spores reported, Petersen's unquestionably belongs to 

 a species of Olpidiopsis. He himself suggests that it may be identical 

 with O. vexans and that the smaller size he reports may result from 

 poor nutritional conditions within the host. 



When more information concerning the sporangial stage is available, 

 Cornu's species can be redefined. Meanwhile, the present writer has 

 compiled a fuller diagnosis, x from the observations since that earlier 

 time. The diagnosis and the occurrences involved are cited below. 



Sporangia spherical or ellipsoidal, from one to six, lying loosely in 

 intercalary and terminal swellings of the host hypha, wall thin, smooth, 

 colorless, with from one to two discharge tubes; zoospores somewhat 

 ovoid, flattened, with two laterally attached flagella, upon escape soon 

 coming to rest in a group, assuming motility after from four to five 

 minutes, and dispersing; resting spore spherical, with a thin or somewhat 

 thickened (brownish?) wall covered with short spines or warts, with or 

 without a companion cell. 



1 Karling (1942e) also supplies a composite description. He believes the species 

 includes Olpidiopsis luxurians Barrett. 



