PEACH DISEASES 281 
the spring rains at a time when the buds swell, and that the 
germtube penetrates the very young leaf as it emerges from 
the bud. This opinion is based on the following circumstantial 
evidence: (1) lesions appear on leaves just as they are pro- 
truding from the buds; (2) leaves from buds sprayed before 
such buds swell show little or no infection during the season, 
while unsprayed buds on the same tree curl badly; (3) buds 
sprayed after they swell, and especially after rains, show curled 
leaves ; (4) the disease occurs only during cold, wet springs. 
From the above data it may be said that, theoretically, 
some sort of spores are lodged by the wind or rains among the 
hairs of the bud-scales during the late summer, and that these 
spores remain there dormant until conditions favorable to 
infection arise the following spring. 
The effect of the environment upon this disease is very 
marked. ‘This is noticed in a general way in connection with 
the geographical range of the disease, which is most common 
and severe in the neighborhood of large bodies of water. The 
combination of conditions most favorable to an epiphytotic 
of peach leaf-curl is a cold wet-period following warm spring 
weather. Warm weather starts the buds; a cold wet spell 
immediately following results in a saturation of the leaf-tissue 
with water, due to a lowering of the temperature and to the 
high humidity of the atmosphere. The buds are retarded, their 
cells gorged with water, and their walls distended, while the 
damp atmosphere permits spore-germination and_ infection. 
As already noted, curl is most severe near large bodies of water ; 
this is doubtless due to the increased humidity of the air in 
these localities, and to reduced temperature in the early spring 
as evidenced by the more frequent occurrence of fogs in such 
regions. Heavy dews can exert but little influence on curl, 
since the moisture and temperature factors are not sufficiently 
pronounced nor of adequate duration to effect a response on 
the part of the host and the parasite. Rainfall seems to have 
