12 



THE WESTERN HEMLOCK. 



conio up beneath a heavy .stand of mature timl^er. Hemlock and 

 Cedar thrive under cover and, where climate and soil are favorable, 

 occur in stands containing- trees differing- widely in age, since 3'oung 

 trees are continually growing up to replace those which die and are 

 blown down. In a forest of Red Fir, however, the trees are practi- 

 callj' of the same age and no reproduction takes place until a large 

 proportion of them are removed and light is freely admitted to the 

 ground. This is usualh^ accomplished by lire. 



Where, as is frequent, the forest consists of an upper story of large 

 Fir and a lower stovy of Hemlock of varying age, it often occurs that 



Ic'J J 40 /6J 



AGL-YLAR3 

 Fig. 1.— Diagram showing lieight growth of mature Red Fir and of Hemlock growing beneath it, 

 calculated on a basis of age. 



as the Fir dies the Hemlock gradually takes its place. Where Fir is 

 killed out by conk or ground- rot, the process is often rapid; and exami- 

 nation shows that the small areas stocked with a pure growth of young 

 Hemlock, so often seen in the midst of a Fir forest, were often caused 

 by this means. It is proba})le that disease in the old Red Fir forests 

 is largely responsible for the present distribution of Hemlock in 

 W^ashington and Oregon. 



(JKOWTH UNDER COVER, 



No tree grows as rapidly in the shade as it does in the light, and 

 Hemlock which has come in under Fir shows a close and often very 



