WILLOW FAMILY 



perhaps better known when, forming a little thicket, it makes 

 a mass of trembling leaves on a gravelly hank hy the road- 

 side, or skirts the border of a swaai|), or forms the first 

 growth on drv npland which has been swept by fire. Under 

 favorable conditions it becomes a tree fifty feet in height 

 and in the mountains of Arizona will reach one hundred feet. 

 Small and quivering leaves necessarily make a tree look 

 fragile and it is doubtful if any size could take from it the 

 appearance of weakness which is its marked cliaractcristic. 



The trunk is slender, the head round-topped, the bark 

 pale green becoming whitish and blotched and marred with 

 age. The leaf is ahiiost round, with a slightly heart-shaped 

 base, serrate margin and acute apex. It comes out of the 

 bud involute, pale green, shining and downy, but finally be- 

 comes smooth and firm in texture, dark green above and dull 

 3'ellow green beneath. The seeds ripen in May and bv 

 means ot the long white hairs which surround them are 

 borne bv the winds to a considerable distance from the 

 parent tree. 



ranges from Hudson's Bay to Mexico. It grows farther 

 n-^rth than the spruce and the larch, and nourishes on the 

 mountain ranges of Chihuahua. 



Professor Sargent says : " The great value of the Aspen 

 hes in the power of its small seeds, supported by their long 

 hairs and wafted far and near by the wind, to germinate 

 quickly in soil Vidiich fire has rendered infertile ; and in the 

 ability of the seedling plants to grow rapidly in exposed 

 situations. Preventing the washing away of the soil from 

 steep mountain slopes and affording shelter for the young of 

 longer-lived trees, it has played a chief part in determining 

 the composition and distribution of the subalpine forests of 

 western America and in recent years it has spread over vast 

 areas of the slopes of the Rocky Mountains from which fire 

 had swept the coniferous trees." Loudon considers our 

 American Aspen to be but a variety of the .Aspen of Europe, 

 Popiihii tie nulla. 



There lingers m Scotland, it is said, the belief that the 



416 



