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12 BULLETIN 879, XT. S. DEPARTMENT OE AGRICULTURE. 
Another symptom on the older leaves which is more common in the 
greenhouse than in the field, consists of a 3-ellowing which affects 
nearly all the leaf at the same time. In such leaves the tissues 
adjoining the larger veins retain their color longest and outline these 
veins against the yellow of the remainder of the leaf. These symp- H 
toms are usually associated with the wilting type of the disease. 
Leaf symptoms on muskmelons.— -The leaf symptoms on the musk- 
melon {Cucumis melo) are very similar to those on the cucumber. 
The first signs of the disease appear on the youngest leaves, which 
turn light yellow in color and develop a sharp downward curl. Later, 
all the younger leaves of the plant show typical mosaic characters 
(PI. V, B). The light yellow portions of the leaf are of irregular 
outline and about the same size and color as those on the young leaves 
of the cucumber. The dark areas are more definitely outlined on 
the muskmelon, and the leaves show a very pronounced curling. 
The characteristic -symptoms found on the older leaves of the cucum- 
ber are much less common on the muskmelon. The older leaves 
gradually become yellow, but show little or none of the tendency to 
die early which appears in mosaic cucumber leaves of the same age. 
Leaf symptoms on squashes. — In the case of the squash {Cucurbita 
spp.) the symptoms of the disease are much the same on all varieties. 
The younger leaves usually develop an extremely savoyed appear- 
ance, the darker parts of the leaf being much more definitely raised 
above the leaf surface than in the case of the cucumber. The light 
spots on the leaf are pale yellowish green and tend to coalesce and 
form a few large blotches rather than the smaller and more numerous 
spots found on the cucumber (PI. VI, A). The older leaves often 
become yellow and gradually die ofT, as in the case of the cucumber, 
but in many plants these leaves will retain their normal color fort' 
some time, the symptoms of the disease being confined to the younger 
leaves. The most marked symptoms have been found on the Summer 
Crookneck and Cocozelle bush varieties {Cucurbita pepo var. condensa) , 
those of the Hubbard type {Cucurbita maxima) showing the disease 
in a less extreme form. 
Leaf symptoms on pumpkins. — On the pumpkin {Cucurbita pepo) 
the leaf symptoms are very nearly identical with those found on the 
squash. The younger leaves develop with the same extreme mottled 
and wrinkled appearance, the general color of the leaf being a lighter 
yellow than that of a normal plant. On the pumpkin, however, the 
older leaves very often show a rapid yellow ing and wilting which corre- ^ 
sponds very closely to that found on the cucumber in the greenhouse. 
Leaf symptoms on other cucurbits. — The general symptoms on the 
gourds and other ornamental cucurbits' are very similar to those on 
the squash. The chief points of difference occur in the patterns of 
the mottled leaves. In the case of the Cucurbita gourds the surface 
