54 



STUDIES OF TREES 



down. It grows to very large size and forms an irregular, 

 wide-spreading, broad head, which is characteristically 

 different from that of any of the other poplars. 



The quaking aspen (Populus tremuloides) , the large- 

 toothed aspen (Populus grandidentata) and the balsam pop- 

 lar or balm of Gilead (Populus balsamifera) are other com- 



FIG. 43. Bark of the Silver Poplar. 



mon members of the poplar group. The quaking aspen 

 may be told by its reddish-brown twigs, narrow sharp- 

 pointed buds, and by its small finely toothed leaves. The 

 large-toothed aspen has thicker and rather downy buds 

 and broader and more widely toothed leaves. The balsam 

 poplar has a large bud thickly covered with a sticky, pun- 

 gent, gelatinous substance. 



