62 PROTISTS AND DISEASE 



resting spores are spinous and have an appendage cell, 

 denoting a zygospore. In Pseudolpidium, e.g. Ps. Pythii, 

 there is no appendage cell. In all these three groups all 

 stages of development from zoospore to sporangium or 

 sorus, i.e. group of sporangia, or to a resting-spore can be 

 traced, because the parasite-plasm remains separate from 

 the host-plasm, and the sporangia are separated by an 

 interval from the cell- wall of the host. 



Very different is the case of Bozella, Fig. 3, D, E 9 where 

 the individuality of the parasite is lost and its plasm finally 

 replaces that of the host, of which the cell- wall is inseparable 

 from that of the parasitic sporangium. The genus Pleol- 

 pidium was made by Fischer for several species of Rozella. 



Woronina, named after the Russian botanist, appears to 

 differ from Rozella in that its sori lie free in the host-cells. 

 After the entrance of a single zoospore into a Saprolegnia 

 from 2 to 14 sporanges of Rozella have been seen to arise. 



Plasmodium-formation. A true union of the bodies of 

 several parasites appears to occur in both Woronina and 

 Rozella, but even in these genera this fusion is apparently 

 not a constant occurrence. 



When the plasmodium is formed it behaves like a single 

 organism, becoming either a single sporangium or a sorus 

 or a resting spore. In the case of Rozella an additional 

 point of interest is seen ; the parasite fuses so completely 

 with the host-plasm that, according to Fischer, another 

 kind of plasmodium is produced. 



