826 



AQUATIC PHYCOMYCETES 



mm. 



Fig. 64. Aphanomycopsis bacillariacearum Scherffel in diatoms 



A. Two discharge tubes emerged from a frustule of Pinnularia, one with a 

 group of encysted primary zoospores. B. Cyst of primary zoospore from 

 which secondary zoospore is beginning to emerge. C. Side view of secondary 

 zoospore. D. Diatom cleared to show endobiotic thallus, and thick-walled 

 "forcing apparatus" at base of long extramatrical discharge tube. E. Diatom 

 on outer surface of which are three encysted zoospores; within a somewhat 

 swollen tubular rudimentary oogonium are two immature oospores, and a 

 third oospore to the right is partly masked by disintegrating host contents. 



(Scherffel, 1925a) 



Parasitic in Pinnularia viridis, Epithemia turgida, rarely in Cymbella 

 gastroides, Nitzschia sigmoidea, Scherffel {loc. cit.), Hungary; Pinnu- 

 laria sp., Sparrow (1933c: 530, pi. 49, fig. 14), pennate diatom, Sparrow 

 and Barr (1955: 555), United States; Synedra sp., Sparrow (1936a: 

 461), Great Britain; Pinnularia viridis, Friedmann (1953: 7), Austria. 



Tokunaga (1934a: 230, fig. 3 a-c) identified with this species a parasite 

 of diatoms in Japan which, though resembling it in its sporangial stage 



