88 



PROTJSTS AND DISEASE 



The three nucleoli seen in Fig. 23, d, have probably arisen 

 from the division of a single nucleolus and have become 

 separated by the formation from their own substance of 



f 



FIG. 23. DETAILS OF A SPECIES OF SYNCHYTRIUM IN A THISTLE-LEAF. 

 a, sorus subdivided into sporangia ; 6, a soral sporangium, zoospores 

 nearly formed ; c, early stage of direct sporangium ; d, part of c 

 more magnified showing three nucleoli ; e, a single nucleolus still 

 more magnified ; /, a stage later than d, a single nucleolus and grains 

 of chromatin in a finely granular plasm ; g, a stage later than /, proto- 

 plasm segmented prior to zoospore-formation ; h, direct sporangium ; 

 i, part of h more magnified, zoospores. Magnification : a, c, and h, 

 X 80 ; b, d, /, g, and *, X 1000 ; e, X 1500. 



new reticular plasmodium. One of the nucleoli, the upper- 

 most in d, has a projection not quite separated from the rest. 

 Assuming that both the soral and the direct sporangia 

 of the thistle- Synchytrium belong to the same parasite, an 

 assumption that makes no difference in regard to the cyto- 

 logical points to be considered, we may compare some 



