PLATE VII 

 Phytophthora infestarus: Infection of potato plants 



Fig. I. — A hill of potatoes having 13 shoots grown from a whole infected tuber in 

 the field. The smallest shoot, indicated by the arrow, became infected by the myce- 

 lium growing up through the stem from the parent tuber. 



Fig. 2. — In this hill with two shoots the fungus has reached the smface and killed 

 its host. 



Fig. 3. — This shows the hill ilktstrated in Plate VII, fig. 2, in its position in the row 

 where it grew. Notice the poor stand obtained by planting infected seed potatoes. 

 This hill did not become a center for the spread of P. infestans, owing to its isolation 

 in the row and early occurrence. 

 5771°— 15 4 



