ROCK WILLOW 



Salix petrophila Rydberg 



This diminutive willow occurs on mountain slopes where other 

 species of willow also flourish, but grows only four or five inches 

 tall, and has the appearance rather of an herb than of a shrub. As soon 

 as the overlying blanket of snow melts, the stems come to life. When 

 the catkins are fully developed, the whole plant is very lovely, and 

 attracts many small bees and other insects. The pollen falls in a golden 

 shower when the branches are shaken. The pistillate flowers develop 

 rapidly into silky heads during the long days of sunshine in June and 

 July. The silk-tipped seeds, loosening from the split pods, are then 

 blown by the wind to a new location. 



Rock willow occurs on alpine peaks from New Mexico to Cali- 

 fornia and north to British Columbia and Mackenzie. 



The specimen sketched was found on the slopes of Mt. Wapta 

 near Burgess Pass, seven miles by trail from Field, British Columbia, 

 at an altitude of 7,000 feet 



PLATE I06 



