THE COXH'EROUS FORESTS Ol' EASTERN NORTH AMERICA. 6 I 



They have much in common in general appearance, mature 

 trees being as a rule spindle-shaped or narrowly conical in 

 outline, with more or less deflexed branches, and leaves an inch 

 or less in length. The tamarack is deciduous, and the rest 

 evergreen. 



Forests of similar aspect, and made up mostly of trees of the 

 same genera, cover large areas in all the cooler parts of the 

 northern hemisphere. Doubtless on account of the abundance 

 of such trees in northern Europe, where most of our Anglo- 

 Saxon traditions orginated, the spindle-shaped tree has become 

 firmly established as the conventional type of conifer. Illus- 

 trations of these trees in their native haunts abound in 

 publications dealing with outdoor life in the extreme northern 

 states and Canada, printed since the invention of the half-tone 

 process, about thirty years ago. 



In the United States the Jack pine prefers coarse sand, and 

 the other trees above mentioned are found mainly in peat bogs ; 

 but farther north they may grow in almost any kind of soil, wet 

 or dry. (In Alaska, even some of the glaciers are said to be 

 partly covered with spruce forests.) The regions where they 

 grow are characterised by cool and moderately humid climates, 

 with an average temperature of 45' F. or less, and an average 

 growing season {i.e., period free from killing frosts) of not more 

 than 150 days. The ground freezes several feet deep in winter, 

 and temperatures of - 30° F. or lower are likely to be experienced 

 by each tree many times during its life. 



The average annual precipitation is 20 inches or more, and in 

 most places in the boreal conifer region there is more of it in 

 summer than in winter, which tends to keep the soil moist 

 throughout the year. 



A climatic factor which involves both temperature and 

 precipitation is the amount of snowfall ; and it appears from 

 statistics of the snowfall of the United States recently published 

 that the type of forest under consideration can be correlated 

 pretty closely with an average annual snowfall of 50 inches and 

 upward. Although it would not be exactly correct from a 

 biological standpoint to say that the narrow conical form of these 

 trees is an adaptation to heavy snows, like the steep roofs of 

 Norway, for example, it would be difficult to imagine any other 

 form of evergreen tree with the same amount of wood and 

 foliage which would be less liable to injury from snow and ice 



