PLATE i 
Puccinia graminis triticiy form III on Baart 
A. —Seven days after inoculation. Longitudinal section of stoma bearing appres- 
sorium. Central part of guard cell dying. X 730. 
B. —From infection seven days old. Haustorium at a and hyphae at b nearly 
empty. X 1130- 
C. —Seven-day infection. Haustorium at b showing nuclei. Modified haustorium 
mother cell at a. X 1130. 
D. —Seven-day infection. Haustoria at c and d, connected by narrow necks to 
the modified mother cells at b and a. X 1130. 
E. —Ten-day infection. Nearly empty hyphae at 6, and partly drained haustorium 
at a. X 1130. 
F. —Seven-day infection. Portion of young uredinium forming under a stoma. 
Young spores and their stalks dense in cytoplasm, while the mycelium farther back 
is drained. X 333- 
G. —Fourteen-day infection. Narrow strip through the center of an infection bear¬ 
ing spores on both surfaces of the leaf. The heavy mycelium ife drained throughout. 
Host cells often are crowded out of shape or even obliterated. X 333. 
