242 
Journal of Agricultural Research voi. xxra, no. 4 
RELATIONSHIP OF CONIDIUM PRODUCTION TO ENVIRONMENTAL CONDITIONS 
After the infected com plant has developed the peculiar yellowish 
white markings which are characteristic of the disease, the production of 
conidiophores and conidia on these areas begins. Just how soon this can 
occur has not been determined; but in most of the cases observed, in 
Fig. i.—D iagrams (from tracings) showing the characteristic configuration and extent of the etiolated 
conidiophore-bearing areas on successive leaves of conspicuously diseased maize plants (A, plant 1; 
B, plant 10, Table II). The etiolated area (white) is increasingly greater and the unaffected area (black) 
increasingly smaller on successively developed leaves. The proportion of the total surface which pro¬ 
duces conidia is relatively large. Scale in inches. 
which the paling of the symptomatic markings took place at night or in 
the early morning, conidium production from these diseased areas began 
the next night if environmental conditions were immediately favorable. 
Under less favorable circumstances, however, several nights sometimes 
elapsed before conidia were produced. 
