Dec. io ( 1917 
Flaxwilt 
585 
Fig. 8 .—A, Longitudinal section of the cortical parenchyma of a resistant flax root showing the formation 
of cork walls around the point of invasion by Fusarium Uni. B, Longitudinal section of the cortical paren¬ 
chyma of a resistant flax root showing a cork layer formed between the point of invasion and the vascular 
system. Notice the increased cell division beneath the cork layer. C, Longitudinal section of the cortical 
parenchyma of a resistant flax ro©t showing cell-wall penetration by F. Uni and the formation of cork walls 
between the invading hypha and the vascular system of the root. The protoplasm in the cork cells was 
granular as indicated by stipling. D, Cross section of the cortical parenchyma of a resistant flax root 
showing the heavy cork walls formed around the point of invasion by F. Uni. Camera-lucida drawings. 
