Amount of Moisture Lost in Winter. 17 
twigs from the same trees and from the same parts 
of the trees, and estimated the percentage of moisture 
again, the object being to determine if the twigs 
contained less moisture after several days of con- 
tinued freezing than they did a short time later, dur- 
ing a thaw. The last two columns of figures in the 
table (pages 14 and 15) are upon this subject. 
The average water content of those twigs cut dur- 
ing a freeze was 47.27 per cent, while that of those 
eut later, during a thaw, was 48.40 per cent, being 
an increase of 1.13 per cent, even though the trees 
had been constantly losing moisture by evaporation. 
Therefore I conclude that during every thaw in 
winter, the tree top fills with sap, and then if a 
sudden severe freeze comes, we are likely to have 
injured trees, due, no doubt, to the sudden freezing 
of the sap, and to the loss of moisture when none 
can be supplied. 
“Tt will be interesting to ecaleulate what weight 
of moisture a tree may lose in winter. <A certain 
soft maple, standing 30 to 35 feet high, with a trunk 
of 15 to 18 inches in diameter near the ground, ex- 
poses from 750 to S800 square feet of surface, and 
loses daily by evaporation from 170 to 180 grams 
of moisture. <A given elm tree, 12 to 15 inches in 
diameter at the base, possesses some 3800 to 400 
square feet of surface, and loses daily from 70 to 
100 grams of moisture. An apple tree 30 years old, 
with a trunk 15 inches in diameter, with a dense, 
bushy top, possesses approximately from 800 to 1,000 
square feet of surface, and loses daily from 275 to 
Cc 
