May, 1923] HARTER AND WEIMER — PECTINASE AND INFECTION 
257 
comes in contact with the living cells of the host, dissolves the middle 
lamellae; the cells then die, and a suitable substance for the further develop¬ 
ment of the fungus is provided. 
2. The practical significance of these results is that wounding is a pre¬ 
liminary necessity to infection. Although sweet potatoes are necessarily 
wounded at digging time when they are broken from the stem, other wounds 
made by rough handling during harvesting, storing, and preparing for the 
market should be avoided as much as possible. 
U. S. Department of Agriculture, 
Washington, D. C. 
LITERATURE CITED 
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