Mar. 6,1917 
Little-Leaf of the Vine 
389 
The St. vineyard consisted of old Tokay vines; the F. vineyard of 
young (5 years old in 1910) Zinfandel vines grafted on Rupestris St. 
George. In the F. vineyard, there was marked improvement in 1911, 
and a slight relapse during subsequent years. 
The sequence of the symptoms during the year is peculiar. All vines, 
except those very badly affected, appear perfectly healthy during the 
early spring. It is only when the weather becomes warm, usually in 
May, June, or July, that the symptoms become marked. They increase 
until about the commencement of the vintage. At this time they com¬ 
mence to disappear and moderately affected vines may appear perfectly 
healthy in October and November. The healthy character of the first 
growth is indicated in Plate 89, B. The leaves on the lower part of the 
canes appear quite healthy. These are the first leaves formed in the 
spring. The disease became noticeable about the time of the appearance 
of the blossoms; and the result is shown in the small, abortive berries 
and the small leaves on the upper parts of the canes. 
SYMPTOMS OF LITTLE-LEAF 
leaves 
Slightly affected leaves are of normal size, or nearly so, but show a 
tendency to curl up at the edges. They show bands or patches of light- 
colored parenchyma. The rest of the leaf appears somewhat darker than 
normal, but this may be the effect of contrast. Such leaves appear on 
very slightly affected vines or at the bases of canes more badly affected 
(PI. 90 ,B). 
More badly affected leaves are smaller and the bands of light colored 
parenchyma are larger and more numerous. These bands are not regu¬ 
lar nor distinctly marked, but cause the general color of the foliage of a 
diseased vine to be lighter than that of a healthy one. Such leaves occur 
chiefly on the middle portions of the canes. 
In very badly affected leaves these symptoms are intensified, and the 
light yellowish bands or spots dry, turn brown, and crack. When the 
canes are shaken, the leaves make a sound like dry leaves. They are so 
brittle that when folded they crack. The petioles are abnormally short 
and thick. 
The microscopical examination of sections showed very little difference 
except a scarcity of chlorophyll grains in the diseased leaves. Though 
these feel thicker, micrometric observations showed that they were 
actually thinner than the corresponding healthy leaves. Ninety-three 
measurements of healthy and diseased leaves gave an average thickness 
of 194.3 fi for the former and 170.2 for the latter. These measure¬ 
ments were made on Feher Szagos and Zinfandel. 
The shape of the leaf is not altered. A large number of measure¬ 
ments showed no change in the ratio of length to width. 
