58 Report OF THE BOTANIST. 
I. FROST BLISTERS ON APPLE AND QUINCE LEAVES. 
DESCRIPTION OF THE TROUBLE. 
During the past season an unusual and interesting disorder of 
apple leaves occurred throughout the greater part of New York 
State. About June 1 the Experiment Station began to receive 
inquiries from orchardists concerning a wrinkling and distortion 
of apple leaves. In a general way the affected leaves resembled 
peach leaves affected with leaf curl; so much so, in fact, that 
several persons inquired if the two troubles were not identical. 
On the upper surface the leaves were variously wrinkled and 
puckered, but the under surface was fairly even and normal in 
appearance except for certain areas on which the color was gray 
ereen (Plates I and II). On some trees the leaves were badly 
distorted, with the margins drawn downward and together as if 
they were unable to unfold properly. Usually the wrinkles were 
most abundant along the mid-rib of the leaf and the elevated por- 
tions were of a somewhat lighter green than other parts of the 
leaf. By cutting across the leaf with scissors it was found that 
where the wrinkles occur the lower epidermis is separated from 
the green pulpy tissue (mesophyll), thus forming a large interior 
cavity or blister (Plate III, Fig. 1). The distance between the 
green tissue and the loosened epidermis was frequently as much 
as four millimeters (one-sixth of an inch), and the blisters thus 
formed were of all sizes up to those having an area of 100 square 
millimeters or even more. In many cases the separated epider- 
mis became ruptured as if slit with a knife, leaving the cells of 
the mesophyll exposed. Sometimes the tender cells thus exposed 
died, causing the formation of an irregular, dead, brown spot, 
visible on both surfaces of the leaf (Plate II, Fig. 4). However, 
in the majority of cases the exposed cells remained green 
throughout the season. 
This condition of apple foliage appears to have been general 
throughout New York State except in the Hudson Valley and 
on Long Island, where it was wholly absent. According to the 
reports of numerous correspondents in various parts of the 
State the varieties Rhode Island Greening, Baldwin and King 
were most affected. Observations made in the Station orchard 
