New York AGRICULTURAL EXPERIMENT STATION. 243 
FROST INJURY. 
Frost causes a very similar russeting of th: fruit; and injury 
from the two causes is often confused. Usually it is not diffi- 
cult to distinguish between them, however. Frost russeting on 
fruit nearly always appears in bands or zones of -greater or 
less width running around the fruit midway between base and 
apex. Whenever russeted fruits in any considerable number show 
this banded appearance it is safe to attribute the injury to frost. 
In most cases, too, the corky, russeted layer is not so thick and 
is smoother, there being far less of the tissue injured. Frost injury 
is not commonly found on many fruits in an orchard and is usually 
confined to certain trees in a low, frosty situation, or the limbs of 
a tree most exposed to frost action. Frost injury on the fruit is 
almost always associated with some injury from the same source 
on the foliage and this is radically different from bordeaux injury 
of the foliage. 
Stewart and Eustace™ of this Station, describe frost injury on 
the foliage as follows: 
“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- 
green. 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 portions were of a 
somewhat lighter green than the 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. The distance between the green tissue and the loosened 
epidermis was frequently aS much as four millimeters (one-sixtn 
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 epidermis became ruptured as if slit 
with a knife, leaving the cells of the mesophyll exposed. Some- 
times the tender cells thus exposed died, causing the formation 
of an irregular, dead, brown spot, visible on both surfaces of the 
leaf. However, in the majority of cases the exposed cells re- 
mained green throughout the season.” 
Stewart and Eustace (58, p. 218). 
