CHYTRIDIALES 67 



II. Mature thallus dividing to form a sorus of sporangia or resting spores, 

 or functioning in its entirety as a resting spore. 



A. Sporangia short-cylindrical, lying in a single row, filling the lumen 



of the host hypha; resting spores lying free as isolated, spiny 

 spheres; each resting spore resulting from the transformation of 

 an entire thallus. 



3. Rozella, p. 68 



B. Sporangia globose, lying free in the host cell and constituting a 



loose aggregation of indefinite form; resting spores similarly 

 arranged or fused to form a warty cystosorus. 



4. Woronina, p. 69 



1. Pseudolpidium Fischer (1892: 33). 



syn. Olpidiopsis (Cornu) Schroter (1892: 69). 



Sporangium smooth-walled; resting spore spiny; companion 

 cell lacking; swarmspores biciliate. 



This genus and Olpidiopsis differ from Olpidium and Pseudolpi- 

 diopsis respectively of the following family chiefly in the biciliate 

 character of their swarmspores. They are said to agree with the 

 other members of the Woroninaceae in the absence of a membrane 

 on the young thallus, but this point has not been thoroughly 

 demonstrated. As the number of ciha on the swarmspore may be 

 determined with certainty only in favorable material the separa- 

 tion of species of these corresponding genera involves accurate 

 observation. A discussion of the interrelationships of the four 

 genera is given below under Olpidium. The following are the 

 best known species of Pseudolpidium. 



P. saprolegniae (Braun) Fischer — in Saprolegnia. 

 P. fusiforme (Cornu) Fischer — in Achlya. 

 P. aphanomycis (Cornu) Fischer — in Aphanomyces. 

 P. pythii Butler — in Pythium. 



2. Olpidiopsis (Cornu) Fischer (1892: 37). 



syn. Diplophysa Schroter, subgenus Euolpidiopsis Fischer 

 (in Schroter 1892: 85). 

 Sporangium smooth-walled; resting spore tuberculate or spiny; 

 companion cell present; swarmspores biciliate; all known species 

 parasitic in Saprolegniaceae. 



The following species have been critically studied. 



0. saprolegniae Cornu— in Saprolegnia (Fig. 7, e). 



0. vexans Barrett — in Saprolegnia (Fig. 7, a-d). 



O. minor Fischer— in Achyla. 



O. aphanomycis Cornu — in Aphanomyces. 



O. luxurians Barrett — in Aphanomyces. 



