56 



PROTISTS AND DISEASE 



allied to Pyihium in organisation, which attacks single cells 

 of algae, sending out rhizoids that pierce adjoining cells. 



Olpidiaceae agree with Synchytriaceae in other ways 

 besides the absence of mycelium ; and a descent from an 

 alga such as Pleurococcus has been suggested ; a view that 

 has some confirmation for Synchytriaceae in features of 

 the parasitic alga Rhodochytrium, see above p. 27. 



FIG. 13. DIAGRAM OF POLYPHAGUS EUGLENAE AS SEEN ALIVE. The 

 small circles represent encysted Euglenae on which, the fungus feeds. 

 1 , mycelial stage ; 2, sporangium with empty section of mycelium ; 

 8, conjugation, the lower plant is the male, the upper the female ; 

 commencing zygospore at Z ; 4, the ripe zygospore with parts of 

 empty tubes ; 5, germination of zygospore, sporangium forming ; 

 6, zoospore. Modified from de Bary after Nowakowski. 



Rhizidiaceae. The first order is illustrated by Polyphagus 

 euglenae. In this organism, Fig. 13, the zoospore, after a 

 dancing motion of about a quarter of an hour, becomes 

 amoeboid, and sends out " rhizoids," resembling filamentous 

 pseudopodia. The organism creeps about until one or 

 more of the rhizoids find an encysted Euglena viridis this 



