INSECT POLLINATION OF FRASERA STENOSEPALA 487 



INSECT POLLINATION OF FRASERA STENOSEPALA. 



L. A. KENOYER. 



One of the largest of herbaceous plants growing- at Tolland, 

 Colorado, 9,000 feet above sea level, is the green gentian, Fras- 

 era stenosepala. X rosette of basal leaves gives rise to a coarse 

 stalk, three to four feet high, with whorls of large leaves and 

 a leafy panicle of rather large flowers of a light green color. 

 Singularly the color is about as inconspicuous as can be 

 imagined. The flowers are rendered rather noticeable by the 

 size and isolation of the plants, but much less so by color. Yet 

 it appeared to surpass all other flowers of the region in the 

 number and variety of insect visitors. The yellow Thermopsis 

 ddvaricata or mountain pea is abundant where Frasera grows. 

 It has a color that renders it visible at a much greater distance 

 than is Frasera, yet it is much less frequently visited by in- 

 sects. 



A casual study of the Frasera blossom show r s, as its principal 

 attraction to bees, two trough-like nectaries which lie on the 

 inner face of the petal, extending almost half its length, and 

 protected against the weather and against small insects by a 

 fringe of hairs on either side of each trough. Bumble bees that 

 visit the flower pass successively to its nectaries, passing the 

 tongue through each. In so doing they rub against the stamens 

 and the pistils in such a way that they could easily effect pol- 

 lination. 



At a number of times during the latter part of June and 

 the early part of July, 1915, insects were captured from the 

 blossoms. Determinations made through the courtesy of Dr. 

 T. D. A. Cockerell of the University of Colorado, show them 

 to be as follows: 



Bombus edwardsii bifarius Cresson. 



Bombus edw r ardsii kenoyeri Cockerell (n. var.) 



Bombus rufocinctus astragali Cockerell. 



Bombus appositus Cresson. 



Psithrus insularis Smith. 



