152 OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 
found upon these vines, and it is probable that the hot sun scalds 
the leaves before the water is evaporated." 
“Tt is quite noticeable that leaves exactly similar to those found 
injured in the open vineyard may also be found among the 
scalded ones.” 
Wind.—The effect of wind on the development of the disease I 
have been able to follow closely. I have observed that the disease 
appears under the following climatic conditions: When hot, still 
mornings are followed by stiff breezes, the disease may be ех- 
pected to appear, and if one walks through a vineyard that has 
become affected from this cause, with his eye to the wind, he will 
observe less disease than if he walk before the wind. The vines 
are affected to windward, which would be expected were trans- 
piration difficulties the cause of the disease. 
Soil texture and fertility.—Pierce observes that the rapidity 
with which vines succumb to the California vine disease depends 
upon the physical condition of the soil. Dividing the soils of the 
state into (1) “Heavy soils, including the red and black adobe 
and clay soils; (2) the gravelly soils; (3) the fine loose soils, 
including the sandy loams and the sands and fine sedimentary 
deposits of the river bottoms,"? he finds that “If conditions. 
of age and variety are the same, the power of any vine to 
resist disease is about as follows upon the three classes of soils : 
(1) Least resistance upon coarse gravelly soils; (2) medium 
resistance upon soils of a heavy and compact nature; (3) greatest 
resistance upon level soils which are loose and sandy but not 
infertile."* 
The róle of soil texture on the development of the California 
vine disease I have been able to follow particularly well in one 
instance. Іп a vineyard already old and subject to the daily blast 
of the trade wind, I found that the disease first appeared where 
the soil was heaviest, developing later where an admixture of 
sand and fine gravel made it more open and penetrable, and this 
despite the fact that the free moisture was approximately the. 
same in both cases. 
nts ete irit 
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Morse, Е. W. Loc. cit., 1595. 
2 Loc. cil., 96. 
* Loc. cit., 98. 
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