New York AGRICULTURAL EXPERIMENT STATION. 63 
LATE FROST THE CAUSE. 
It soon became evident to the writers that the blisters were, 
in some way, the result of frost injury. They were plainly not 
the work of fungi or insects. The fact that the trouble was 
widespread suggested the idea that weather conditions were 
responsible for it; and since it was a very unusual phenomenon, 
not having been previously observed in America so far as we 
can learn, the cause should be sought in unusual weather con- 
ditions. The spring of 1902 in New York was unusually wet 
and cool, and there were severe late frosts on May 10 and 11. 
Wet weather might bring about cedema, and apple twigs are 
known to be subject to that trouble?; but that this was not a 
case of wdema is shown by the fact that the mesophyll cells, 
although much elongated as in cedema, were not in contact with 
the epidermis, and therefore could not have exerted any pres- 
sure upon it so as to cause either the wrinkles or the rupturing 
of the epidermis (Plate ITI). 
The theory that the trouble was due to the frosts in May is 
supported by the following facts: (1) Only the early leaves, at 
the base of the shoot, were affected. Leaves formed after the 
frosts were not affected in the least. The frosts occurred while 
the first leaves were partially unfolded, and just before the blos- 
soms opened. (2) It was most common in localities where the 
frosts were most severe, less common where the frosts were 
lighter, and wholly wanting in localities where there was no 
frost, as, for example, on Long Island. At Geneva the tempera- 
ture fell to 27 degrees Fahr. on May 10 and to 26 degrees on 
May 11. Over the greater part of the State temperatures as 
low or lower than these prevailed. The following table, com- 
piled from the May report of the New York section of the 
climate and crop service of the Weather Bureau, shows the 
minimum temperature at the various stations of the bureau 
in New York for May 10 and 11. In each of the two columns 
each temperature given is for a different station. 
2Atkinson, G. F. QC2dema of Apple Trees. Cornell Univ. Agr. Exp. Sta. Bul. 61 : 299-302 
