THE POTATO DISEASE 63 



branch or axis bearing it continues to elongate in the same 

 straight line, leaving the conidium apparently attached to 



Fig. 7. Phytophthora infestans. i, a cluster of conidiophores with 

 conidia, X 400 ; 2, a free conidium showing its contents breaking up 

 into zoospores, x 400 ; 3, a conidium germinating and liberating 

 zoospores, x 400; 4, a zoospore that has become passive and germin- 

 ated, X4oo ; 5, a conidium germinating by the protrusion of a germ-tube, 



its side. After the branch has grown for some time, a 

 second conidium is produced at its tip, to be again left 



