THE MOSAIC DISEASE OE CUCURBITS. 11 
In some cases the green and yellow areas are both small and about 
equal in number (PL III) , being scattered irregularly over the leaf 
and sometimes coalescing to form larger areas, with the green portions 
rather sharply defined, owing to their raised character. More often, 
however, there are a few isolated patches of yellow from 3 to 5 milli- 
meters in diameter, the greater portion of the leaf being dark green 
with the typical savoyed character. On other leaves the yellowing 
may take the form of large blotches which tend to follow the large 
veins, the margins not being sharply defined but blending gradually 
into the green portions of the leaf. In such leaves the savoyed 
appearance is much less marked. 
In the case of older plants the wrinkling of the young leaves is 
usually very noticeable, but there is less contrast in color. The 
raised parts of the leaf are dark green, while the remainder is merely 
a lighter shade of green than that found in normal leaves, the borders 
r of these light spots not being sharply defined. In such plants the 
base of the leaf will occasionally develop a sharply contrasted mosaic 
mottling, while the tips of the leaves will remain normal in color 
for some time. 
In the older leaves the symptoms are somewhat different in nature. 
The savoyed character does not appear in many cases, and the yellow- 
ing tends to include the entire leaf in a short time. In leaves which 
are nearly full grown the yellowing very often extends along the net- 
work of the larger veins of one of the basal lobes. The portions of 
the leaf inclosed within these veins may remain green for some time 
and have a slightly convex appearance. A pronounced drooping 
or curling of the leaf often follows in the parts where such a mottling 
occurs, producing a peculiar wilted appearance in the lobe of the 
%leaf affected. 
In other cases certain portions of the leaf turn yellow and the re- 
mainder retains its green color for a considerable time. The yellow 
portions in such leaves often include a few small, isolated, dark-green 
areas, producing an odd, checkered appearance in these portions of 
the leaf. This is quite distinct from the ordinary mosaic mottling 
in that the green tissues show no tendency to be elevated above the 
surrounding leaf surface. This type of yellowing occurs most com- 
monly in the angle formed by the junction of the large veins at the 
base of the leaf, but also appears at the tips of the lobes. In such 
I leaves the green portions retain their color for some time. One of 
* the most common symptoms in the older leaves of mature plants 
commences as a yellowing which appears along the large lateral 
veins of one of the basal lobes, extending their entire length. These 
yellow areas are widest at the edge of the leaf and narrow toward the 
juncture of the veins, producing V-shaped areas which have already 
been described (PL III). 
