PLATE 2 
A. —Section of wheat stem showing a moderate amount of sclerenchyma fiber 
development. The tissues are as follows: (a) Epidermis, ( b ) collenchyma, (c) scle¬ 
renchyma fibers (X120), (d) thin-walled parenchyma, (e) fibrovascular bundles. 
B. —Section of wheat stem showing a relatively small amount of sclerenchyma 
development in proportion to collenchyma. The tissues are lettered as in A. 
C. —Cross section of upper part of peduncle of Kota wheat, C. I. 5878. The collen¬ 
chyma (c) is restricted to small unit areas separated by the sclerenchymatous fibers 
($). X60. 
D. —Cross section of upper part of peduncle of Little Club wheat, C. I. 4066. The 
collenchyma (c) is almost continous. X60. 
E. —A similar section from the peduncle of Marquis wheat, C. I. 3641, showing a 
moderate amount of sclerenchymatous tissue (s) in proportion to the collenchyma (c). 
X60. 
F. —Cross section of peduncle of Sonem emmer, C. I. 4402. There is a large amount 
of sclerenchymatous tissue (j) in proportion to the collenchyma (c). X60. 
G. —Transverse section of peduncle of Kota wheat, C. I. 5878, infected with Puccinia 
graminis. Note the small uredinium confined to a single collenchyma bundle. 
Lateral spread of rust is impossible because of the strands of sclerenchymatous tissue. 
X45. 
H. —Similar section of peduncle of Little Club wheat, C. I. 4066. Note the very 
large uredinium which probably has resulted from the confluence of several smaller 
ones. Lateral spread of infection is not restricted by sclerenchyma. X45. 
I. —Transverse section of the upper peduncle of Acme wheat, C. I. 5284, showing 
an almost continous band of sclerenchyma just under the epidermis. X200. 
J. —Transverse section of a portion of a typical mature leaf of Haynes Bluestem wheat 
showing restriction of rust mycelium to the chlorenchyma between two fibrovascular 
bundles. X75. 
K. —A similar leaf section from a plant of Haynes Bluestem grown in nitrogen- 
deficient soil. X60. 
L. —Transverse section of a leaf of Haynes Bluestem plant grown in soil containing 
excess nitrogen. X60. 
M. —Transverse section through the midrib of a leaf of a Haynes Bluestem plant 
grown in nitrogen-deficient soil. X45. 
N. —A similar section through the midrib of a leaf of a Haynes Bluestem plant 
grown in soil containing excess nitrogen. X45. 
