70 PROTISTS AND DISEASE 



proliferation of the cells around those that harbour para- 

 sites : small galls, Fig. 18, G, are thus produced. In the 

 common potentil this hypertrophy takes the form of hair- 

 cells. In the potato S. endobioticum causes warty cancer- 

 like tumours. Some kinds of potato are immune, but it 

 is not clear in what this immunity consists. 



The Life-cycle of Synchytrians. The life-C3^cle of 

 Synchytrians varies in different species. In some, such as 

 S. anemones and 8. mercurialis, only resting-cells are 

 formed. 



These are dormant all winter in the decaying remains 

 of the host-plant and germinate in spring, their zoospores 

 entering epidermis cells of young plants. From their 

 condensed life-cycle de Bary named these Pycnochytria. 

 They always pass through a soral stage in germinating. 

 The remainder, or Eusynchytria, have a double cycle, like 

 many Sporozoa. In suitable weather a series of generations 

 follow one another before the resting cells are formed. The 

 Eusynchytria again fall into two groups : in one group, 

 which may, perhaps, be named Pleochytria, and which 

 includes S. stellariae and S. oenotkerae (evening primrose) a 

 sorus is formed in both parts of the cycle : in the other 

 group the sorus is omitted from the germination of the 

 resting cell. To this latter group belong S. taraxaci, S. 

 siiccisae (scabious), and 8. endobioticum, &c. 



8. aureum belongs to the pycno-group, having one 

 brood of swarm-spores in the spring of each year. One 



