8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



lations and stripes, which are more or less yellow the intensity of the 

 colorations depending, it would seem, on the rapidity with which the 

 disease has progressed. The center of the spot now dies, becoming 

 reddish-brown, sometimes almost with a brick tint and a sub-glossy 

 appearance when death has been rapid. According to the rapidity of 

 death these spots or stripes are surrounded, either (a) with a thin 

 border of dull, deep red, which, in turn, is separated by a suffused 

 yellow or greenish-yellow band from the green of the still healthy sur- 

 rounding tissues; or (b) with a border of yellow, either suffused and 

 broad, or thin and with a more definite margin; or (r) directly by 

 the healthy green tissue itself. Sometimes the old leaves near the base 

 of the shoots show a slight variation from the characteristics just 

 described. These leaves, as soon as the disease begins to appear between 

 the veins and the spots enlarge and merge to form stripes, become more 

 or less greenish-yellow in the entire parenchyma. The dead areas, 

 instead of being reddish-brown and in sharp contrast to the living 

 tissues, are fawn-colored and soft, crumbly, tear easily, and fall away. 

 The affected leaves thus become deeply incised, sometimes almost to the 

 petiole, from which they hang in two, three or more pieces. 



In the case just described, as likewise in the preceding, the leaves 

 may remain attached to the shoots for an indefinite time, and when 

 they fall it may be either with the petioles, or before them. 



Effect of the Disease on the Fruit. The fruit of white varieties of 

 grapes appears to be more sensitive to the Red-leaf disease than that 

 of black varieties. It would seem that the latter show the character- 

 istics of this disease more markedly on the foliage, except in severe 

 cases, and toward autumn, whereas in the former the disease is more 

 conspicuous on the berries. 



The Red-leaf disease may affect the fruit soon after setting. When 

 this occurs, on passing the hand over a diseased bunch of grapes, the 

 berries come off either with or without the pedicels. They even fall of 

 themselves, and the stem (peduncle) dries up and falls also. This 

 manifestation of the disease is more frequent among the red than the 

 white grapes. The more noteworthy characters begin to show unmis- 

 takably on the berries when the clusters of grapes are a month or a 

 month and a half old, and only become general just prior to the begin- 

 ning of maturation. The berries become suffused with livid discolora- 

 tions, which are sub-cuticular, the cuticle itself not being affected until 

 later. The tissue of the berries in the center of these spots generally 

 falls away from the epidermis, which then collapses. The livid and 

 sunken spots thus formed may be more or less numerous, and large or 

 small; they are more frequent on the exposed berries than on those in 

 constant shade; they are more frequent on the sides of the berries 

 exposed to the light than on the shady sides. When they do not fall 

 off at this stage, the berries shrivel and dry up. 



