THE TREE. 11 



The Amount of Water Lost by Trees in Winter. After 

 many careful experiments, A. L. Knisely, M.S., concludes 

 that a Soft Maple standing 30 or 35 feet high with a trunk 

 15 to 18 inches in diameter near the ground, exposing from 

 750 to 800 square feet of bark surface, may lose daily by 

 evaporation from 6 to 7 pounds of water when dormant. 

 An Apple-tree 30 years old and 15 inches in diameter at the 

 base, exposing from 800 to 1,000 square feet of bark surface, 

 may lose daily while dormant from 10 to 13 pounds of 

 water. These figures are from results obtained during 

 winter weather in New York, where the relative humidity 

 of the air is higher than in Minnesota, which would lessen 

 evaporation. It is probable that during the winters in 

 Minnesota evaporation from trees will greatly exceed that 

 in New York, and that greater evaporation is nearly always 

 responsible for some trees being tender there and in other 

 places with similar conditions. 



We know that after a prolonged period of severely cold 

 weather the twigs of Soft Maple, Apple, and some other 

 trees, have a decidedly shrivelled appearance which disap- 

 pears after a few days of mild weather. Soft-Maple trees 

 standing on dry land will sometimes in the spring appear to 

 have been dried out and to have become partly or entirely 

 dead. It is probable that during the coldest weather very 

 little, if any, moisture can be supplied from the roots, 

 which may account for this shrivelled condition. 



Second Growth. Sometimes warm, moist weather in late 

 autumn will cause trees to start a strong second growth in 

 October, which draws on the stored plant^food and perhaps 

 exhausts it, and winter sets in before the tissues have again 

 become hard and stored with food. In such cases trees are 

 liable to injury. No characteristic of hardiness is more 

 important in plants than that of early maturity of wood. 



One part of the tree may start into growth without 

 regard to the conditions of the other parts. For instance, 



