ORDEB LAGENIDIALKS 



97 



upon germination gives rise to one zoospore or to several zoospores. The 

 foregoing description applies to Woronina, the type genus of the family, 

 which is parasitic in the hyphae of Saprolegniaceae and in Vaucheria. 

 Two other genera, Rozellopsis, parasitic in Pythiaceae, and Pyrrhosorus, 

 parasitic in Red Seaweeds, are tentatively also placed in this family but 

 differ in not forming clusters of zoosporangia and in their failure to pro- 



FiG. 30. Lagenidiales, Family Woroninaceae. Woronina 

 polycystis Cornu. (A) "Plasmodium" nearly filling host 

 cell. (B) Early stage in the formation of zoosporangia. 

 (C) Empty zoosporangia. (D) Zoospore. (E) Infection 

 of host by zoospore. (F) Cystosori within host. (After 

 Cook and Nicholson: Ann. Botany, 47(188) :851-859.) 



duce cystosori. The vegetative stage within the host is, as in Woronina, 

 more or less plasmodial in nature. (Fig. 30.) 



Family Olpidiopsidaceae. With the removal of Woronina to a dis- 

 tinct family the remainder corresponds in the main to the Woroninaceae 

 of the previous edition. Vegetatively and in their asexual reproduction 

 the members of this family show great similarity to those of the Olpidiaceae 

 in the Chytridiales. They differ strongly, however, in producing zoospores 

 with two anteriorly or laterally attached flagella, one of the tinsel type, 

 the other of the whiplash type, and in possessing walls which give the 



