THE MOSAIC DISEASE OF CUCURBITS. 13 
of the leaf is finely wrinkled and the yellow areas are very small but 
present in large numbers, so that the leaf appears to be covered with 
fine dots of yellow, which in some cases bear a close resemblance to 
insect injury. This type of mosaic symptoms is also common on the 
Luffa and Lagenaria gourds, the spots in the latter species being 
^larger and very nearly circular in form. (PL V, A.) 
On the wild cucumber (Micrampelis lobata) there is usually a 
marked variegation and deformity in the leaves of mosaic plants. 
In most cases the symptoms are similar to those on the cucumber 
with the exception that the lighter colored portions of the leaf pre- 
dominate. These are a light yellowish green with an occasional 
almost colorless area which is in sharp contrast to the surrounding 
tissue. The other parts of the leaf are a deep green and are raised 
above the surrounding surface. As a result the savoyed character is 
usually pronounced, and the leaves are deeply wrinkled and curled. 
^ There is also considerable dwarfing and deformity in mosaic leaves, 
the lobes being irregular in size and outline. In some leaves, how- 
ever, the difference in color in the various parts of the leaf is less 
marked, and in such cases the savoyed character does not appear, 
although the leaf may be distorted in shape. (See PL VII, A, B, 
and C, for comparison.) 
While the above types of symptoms occur most commonly, there 
are often cases in which the greater part of the leaf remains almost a 
normal green but develops numerous small circular areas of light 
yellow which are similar to those noted on the Cucurbita gourds. 
These yellow spots are about 1 millimeter in diameter and are slightly 
depressed. In other leaves we find a number of small, dark-green 
areas scattered over the surface, the center of each of them being 
^composed of a small yellow spot similar to those above described. 
'The green portion of these areas is raised, while the yellow centers 
are slightly sunken, producing a peculiar pitted appearance. 
The older leaves of mosaic plants gradually turn yellow, some of 
them showing the V-shaped yellow patches which occur on the older 
leaves of the cucumber. This yellowing of the leaves eventually 
affects most of the plant and is a distinguishing character of the later 
stages of the disease. 
The symptoms on the other wild host, Sicyos angulatus, are much 
like those on micrampelis. The mottling of the young leaves is 
seldom extreme, but the older leaves tend to yellow and die off rapidly, 
■the dead leaves remaining attached to the stem as in the case of the 
cucumber. 
FRUIT SYMPTOMS. 
Fruit symptoms on cucumbers. -The symptoms on the fruits of the 
cucumber are extremely marked in most cases and when present 
make the disease easily recognized. The stem end of the young 
