ECOLOGY. 349 



instead of flattened, and the number of sterile florets much greater than 

 in the normal ones. A statistical study has been made of the various 

 modifications of spikelet and flower, to determine whether the mutant 

 is gradually reverting to the type, as seems to be suggested by one or 

 two inflorescences. 



Experimental Pollination, hy F. E. Clements and Frances Long. 



Studies have been made throughout the summer on the seasonal 

 succession of insect polhnators on the dominants in the region of the 

 Alpine Laboratory. In this connection, quantitative studies have 

 been made of all the visitors to each dominant for extensive periods. 

 This not only shows the range of species visiting each plant, but also the 

 frequence of the visits of each species, the rate of working, the method 

 of work, and the relative efficiency of each pollinator. Thus, in certain 

 species of Bomhus, it has been found tliat the drones do about twice 

 as much work as the workers. 



Much attention was given to experiments in the competitive rela- 

 tions of flowers to a particular pollinator. Branches or bouquets of 

 one species were placed on a plant of the other in full flower, and vice 

 versa. The competition pairs and groups employed were as follows: 



Rubus strigosus : Rubus deliciosus. 

 Rubus strigosus: Rosa acicularis. 

 Rubus strigosus, Opulaster opulifoHus. 

 Pentstemon gracilis: Pentstemon glaber. 

 Pentstemon glaber: Pentstemon glaucus. 

 Pentstemon glaber: Epilobium spicatum. 

 Pentstemon glaber: P. barbatus, glaucus, and gracilis. 

 Aconitum columbianum: Epilobium spicatum. 

 Aconitum columbianum: Delphinium scopulorum. 

 Monarda fistulosa: Epilobium spicatum. 



With a few exceptions, usually very young or very old bees, even the 

 most conspicuous flower was unable to attract a pollinator from the 

 species it had formed the habit of working on for a particular period, 

 until that species was past its maximum flowering. This was most 

 marked in the case of Apis melUfica, but it was also generally true of 

 several species of Bomhus, Osmia, etc. 



The use of various manipulation devices was continued. These 

 were chiefly false corollas, painted corollas, removal or mutilation of 

 corolla, change of position, etc. The response to these varied greatly 

 with the kind of flower and insect, and sometimes with the kind of 

 day. Monarda furnished a striking instance of the difference between 

 individuals in behavior and of the fixity of habit in certain individuals. 

 In one large group, Bomhus proximus and B. hifarius were robbing the 

 flowers by boring a hole at the base of the corolla tube, while in a 

 smaller patch a few yards away they were working hard to reach the 

 nectar through the throat. When the corolla tubes were cut short in 

 flowers of the first group, both species continued to rob, though they 

 could easily reach the nectar through the tube. 



