28 PROTISTS AND DISEASE 



To the naked eye it appears as a small bright red spot, 

 as told us by B. F. Griggs, some of whose illustrations are 

 copied in Fig. 5. It developes starch abundantly, the grains 

 being built up in the protoplasm as Charpentier found to 

 be the case with Cystococcus. 



The colouring matter is a lipochrome. The plug at the 

 surface end, Fig. 5, C, p, melts away when the ripe sporangium 

 is placed in water. Rhodochytrium is not an intracellular 

 parasite like Woronina and Rozella, but it makes room for 

 itself in the intercellular spaces of the host plant. At its 

 broad deeper end it pushes out rhizoids, which are shut off 

 by septa when the alga becomes either a resting-spore or a 

 zoosporangium. The smallest resting-spore is 70ju long. 

 At maturity the nucleus of the resting-spore shrinks, Fig. 5, 

 B, or collapses, to expand again when the spore germinates 

 in water. The zoosporangium has other peculiar nuclear 

 characters : on entering the host-tissues the nucleus in- 

 creases rapidly in size, from 4 or 5/x in the zoospore to 50 or 

 60 ju, in the zoosporangium ; such a growth of a nucleus is 

 only equalled in Synchytrium. It is not in size alone that 

 the nuclei of Rhodochytrium recall those of Synchytrium : 

 the peculiarly large nucleoli, Fig. 5, D, and the disordered- 

 looking primary mitosis, E, have a likeness to features in 

 Synchytrium. Now, though Rhodochytrium, an intercellular 

 parasite, is different in habit from the intracellular Synchy- 

 trium, these nuclear processes show that there is a probable 

 near kinship. 



