54 
done must be immense. Under ‘such see! 
galvanized iron roofing perforated by hailstones as readily as if it 
had consisted of paper. 
In speaking of the damage done to trees, Hartig says* :—* At 
places where the hailstones strike the rind is crushed, or it may be 
knocked off altogether, Although as a rule, a callus very soon 
forms over such wounds, still it not infrequently happens that the 
were affected by hailstones died—a result doubtless due to the 
excessive evaporation from the wood, which in many cases was 
stripped of its cortex on one side of the shoot to the distance of 
oe . 
Spring frosts.—These are, with much reason, dreaded by those 
relative amount of water present in the 
ear. When active growth 
contain a considerable 
Gitatibporwers During ‘a late spring frost water is abstracted 
from the cells into the intercellular Spaces, more especially under 
the epidermis of leaves and shoots, where it freezes into parallel 
oe crystals. The withdrawal of water from the cells of a 
ace is often completely torn 
. f, and hangs like a. blister. 
abbag: es are often injured in this manner, The young leaves of 
evergreens also suffer M a similar way. : 
in the ba ¥ ; vee These are longitudinal cracks of variable length 
and snd Je bs wood of tree trunk » and are the result of a great 
n lowermg of the temperature. [pn this instance water 18 
Hartig und Somervilie, * Diseases of Troes ” ; Engl. ed., p, 299 (1804). 
