17 



the time was covered with slender green catkins of pistillate 

 flowers. On several branches there were larger, gray catkins — 

 apparently staminate — so different from the others as to be 

 noticeable at a considerable distance. These catkins proved to 



Fig. I. Normal pistillate flower of Popiilus grandidentala. 



be made up of staminate, pistillate, and perfect flowers arranged 

 without any regular order. On some of the catkins staminate 

 flowers predominated, on others pistillate— but most of them were 

 made up almost entirely of perfect flowers. The tree was visited 



