Jul. 1120, U. S. Dept. of Agriculture. 



Plate IV. 



'i 



^ 



Photomicrographs of Cross and Longitudinal Sections of Stems of 

 Heat-Cankered Flax Plants of the Same Age as Those Shown in 

 Plate III. 



A, injured, constricted area of plant. This cross section show.s the entire cortex destroyed. The 

 cortical cells are broken down, but the stelar tissues are still functioning. There is no evidence of 

 fungous mj'cehum in the injured tissues. Compare this with B. B, cross section immediately 

 above the cankered area. AH tissues appear healthy. Compare this with A . C, longitudinal 

 section through the upper portion of an injured, constricted area. This shows the cortex de- 

 stro3'ed in the cankered area. D longitudinal section of a young flax stem immediately above 

 the heat-cankered area. 



