F. T. Brooks. 
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darkening of the hyphae in the cells of these regions. Smaller black 
zones sometimes occur as islands a little distance away from the 
longer lines. Fig. 1 shows a general view of one of these black 
lines in the wood, which are closely similar to the black zones in 
the fructifications, Fig. 5 shows a section through one of these 
black lines seen under the microscope. The brown tissues border¬ 
ing these black lines contain hyaline hyphae which are especially 
F 10 . 5. Ustulina zonata. Section of black zone in diseased wood of Hevta 
brasiliensis taken from the collar of an old tree, x 330. 
abundant in the vessels. It is noteworthy that the black lines often 
occur just within the margin of the region penetrated by the hyphae. 
One one occasion tyloses were found in vessels affected by the 
fungus, but the presence of these ingrowths does not occur regularly 
as in the tissues of Hevea invaded by Corticium sahnonicolor as 
