PLATE i 
A. —Young maize plant (Mangonon White Dent) four days after the first symp¬ 
tomatic paling of the leaves. Conidiophore production which has already taken 
place on two favorable nights has begun characteristically on the distal portion ot 
the upper leaves (a, a). The total conidiophore-bearing area at this early period com¬ 
prises only a few square centimeters but as time goes on will continue to become 
increasingly extensive as the plant develops. XK- 
B. —A near view of the fifth to eighth leaves of a young maize plant (Chinese Waxy 
white), showing (at x, x) the etiolated stripes characteristic of the downy mildew. 
These markings had only begun to turn pale a little before dawn of the morning 
on which they were photographed, hence they were still inconspicuous and free 
from conidiophores. During the succeeding night, however, conidiophores were 
developed on the pallid areas. Natural size. 
C. —Plant of maize (Guam White Flint) which, although only a little over 3 weeks 
old, is already producing vast quantities of conidiophores each favorable night from 
relatively extensive and conspicuously pale areas on its upper leaves and sheaths. 
XX- 
1 The photographs of Plates 1 to 6 were taken by the author. 
