Salicaceae 69 



base, petioles round. Flowers in slender 

 catkins, the staminate and pistillate on 

 separate trees. 



Throughout the region in the river valleys 

 and on the surrounding slopes, usually a tree 

 not over 20-30 feet high but sometimes 

 attaining an immense size. 



Po ulus ^ s ^ enc ^ er ^ ree with smooth, light 



tremuloides green bark, seldom more than 

 Michx. 40-50 feet high, and less than 



American half th&t {n QUr region Leaves 



smooth when young except on 

 the margins, ovate, short- acuminate at the 

 apex, rounded at the base, finely crenulate 

 all around; petioles flattened laterally, very 

 slender, causing the leaves to quiver with 

 the slightest breeze. Flowers in rather 

 stout catkins. 



Frequent in the low valleys and slopes 

 through the Rockies, forming groves, or 

 singly. 



The willows which are very largely repre- 

 sented throughout the region, in the low 



