160 SILVA OF NORTH AMERICA. SALICACEE. 
turnery. In northern British America it is the principal fuel of the Indians, and, as it burns freely 
while green and without sparks, is used in the open fireplaces at the posts of the Hudson Bay 
Company.’ The sweet inner bark in early spring is used as food by the Indians of the north.’ 
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. 
Populus tremuloides, which in habit and general appearance resembles the Old World Populus 
tremula, was introduced into English gardens by Frederick Pursh* in 1812,* but is probably rarely 
cultivated. 
A graceful tree with its slender pendulous branches, shimmering leaves, and pale bark, the Aspen 
enlivens the Spruce forests of the north, and marks steep mountain slopes with broad bands of color, 
light green during the summer and in autumn glowing like gold against backgrounds of dark cliffs and 
stunted Pines. 
1 Richardson, Franklin Jour. Appx. No. 7, 766 (Populus trep- 3 See ii. 39. 
ida); Arctic Searching Exped. ii. 315. 4 Aiton, Hort. Kew. ed. 2, v. 395. 
2 See Holmes, Am. Jour. Pharm. lvi. 619. 
EXPLANATION OF THE PLATE. 
Pirate CCCCLXXXVII. Porunus TREMULOIDES. 
. A flowering branch of the staminate tree, natural size. 
Diagram of a staminate flower. 
. A staminate flower with its scale, enlarged. 
A stamen, enlarged. 
A flowering branch of the pistillate tree, natural size. 
Diagram of a pistillate flower. 
. A pistillate flower with its scale, enlarged. 
. Vertical section of a pistil, enlarged. 
OCWOABDAP WN 
. A fruiting branch, natural size. 
~ 
—) 
. A fruit, enlarged. 
—_ 
ary 
. A fruit with open valves, enlarged. 
fos 
bo 
. A seed, magnified. 
ra 
oo 
. Vertical section of a seed, magnified. 
= 
is 
. An embryo, magnified. 
bab 
OU 
. A winter branch, natural size. 
—_ 
for) 
. A leaf-scar, enlarged. 
