WiLLOW FAMILY 
perhaps better known when, forming a little thicket, it makes 
a mass of trembling leaves ona gravelly bank by the road- 
side, or skirts the border of a swamp, or forms the first 
growth on dry upland 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 characteristic. 
The trunk is slender, the head round-topped, the bark 
pale green becoming whitish and blotched and marred with 
age. The leaf is almost 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 
yellow green beneath. The seeds ripen in May and by 
means of the long white hairs which surround them are 
borne by the winds to a considerable distance from the 
parent tree. 
“ ranges from Hudson’s Bay to Mexico, It grows farther 
north than the spruce and the larch, and flourishes on the 
mountain ranges of Chihuahua. 
Professor Sargent says: “The great value of the Aspen 
lies 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 which 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, 
Populus tremula, 
There lingers in Scotland, it is said, the belief that the 
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