114 OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 
the bunch. This dropping of the fruit is not so strongly marked 
and is less important than the drying of the berry upon the 
bunch. . . . In some cases the growth of the berry is retarded. 
... The drying of the fruit upon the vine is a leading effect of 
the disease and is very general in all varieties and under all 
Conditions "7 
Pierce states that the California vine disease has а period of 
incubation. He says “ In the affected district it is common to find 
a vineyard of one variety looking perfectly healthy and the 
adjoining vineyard of another variety badly affected or killed by 
the disease. It may be that the vines are of the same age and 
upon like soil. When we see a sharp line of this kind,” he con- 
tinues, "drawn between varieties it is folly to say that the 
disease has affected one and not the other, for it may occur that 
the dying variety is found on all sides of the living one. It must 
be admitted, then, that the disease has produced its effect upon 
vines not yet showing those effects." Again, “it is also common 
to find a few Mission vines scattered here and there in vineyards 
of other varieties, they having been planted through oversight and 
the mixing of cuttings. Where this has been the case, these 
Mission vines have been singled out and killed by the disease 25 
surely as if they were by themselves in adjoining vineyards. . - 
The truth is, that all the vines have felt the same influence of the 
disease, but on account of difference in hardiness some show this 
influence earlier than others." Another, and тоге striking 
feature of the malady is the overbearing of the vines “ while the 
disease is incubating.” But overbearing is not a constant symp- 
tom. Pierce notes the fact, and at the same time remarks: 
“That overproduction has not always been noticed is but nega- 
tive evidence, and its well-attested occurrence in a reasonable 
number of cases is of more value than much negative evidence." 
The California vine disease appears also to be transmitted 1n 
cuttings, 
Pierce does not come to any conclusion regarding the nature 
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