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 

 cut 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 

 (ian be supplied. 



"It will be interesting to calculate 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 800 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 300 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 



