828 AQUATIC PHYCOMYCETES 



5-15 u. in diameter; sporangium 5-15 [x in diameter, with one or two 

 discharge tubes 10-185 u. long by 5-8.5 u, in diameter contracted to 2.5 u, 

 where it passes through wall of the host; primary zoospores probably 

 nonflagellate, forming ten to sixty spherical cysts 6-8 \i in diameter at 

 the mouth of the discharge tube, secondary zoospores 8 u. long by 7 [i 

 broad, kidney-shaped with two lateral flagella; resting spores 3-17 form- 

 ed within the thallus, spherical to subspherical, 9-20 u. in diameter, 

 with a thick colorless probably punctate wall, numerous small refractive 

 globules in the contents, germination not observed. 



Parasitic in Netrium digitus, Canter (loc. cit.), Great Britain ; Pleuro- 

 taenium trabecula, Friedmann (1952: 203, fig. 5, 1), Austria. 



Canter's species differs from Aphanomycopsis bacillariacearum in its 

 host, the character of the resting-spore wall, the size of the secondary 

 zoospores, and the lack of a "Spriezapparat" where the discharge tube 

 penetrates the host wall. Friedmann remarks that the desmid parasite 

 figured by Petersen (1910: 556, fig. 26, b) is probably this species. 



IMPERFECTLY KNOWN SPECIES OF APHANOMYCOPSIS 



? Aphanomycopsis sp. Friedmann 

 Osterr. Bot. Zeitschr. 99: 201, figs. 5a-i. 1952 



Sporangium 3.2-8.5 \x in diameter, up to 200 \x long, the main axis 

 lying the length of one of the valves of the host, bearing numerous 

 lateral branches that bend and anastomose to produce a ladder-like 

 structure, wall extremely delicate, quickly disorganizing after spore dis- 

 charge through one to several 7-8 [j. diameter (tapering to 5 u, distally) 

 discharge tubes; primary zoospore cysts 6.5-7 \i in diameter; other 

 features not observed. 



Parasitic in Nitzschia sigmoidea, Austria. 



Differs from Aphanomycopsis bacillariacearum in the delicate walls 

 and ladder-like aspect of the thallus and in the smaller cysts of the 

 primary zoospores. 



THRAUSTOCHYTRIACEAE, emend. 



Thallus epi- and endobiotic, monocentric, eucarpic, chytridiaceous 

 in character, the epibiotic part composed of the sporangium, the endo- 



