48 



NORMAL AND EXPERIMENTAL POLLINATION. 



These results show that the drones of some species of Bombus gather 

 nectar, while among the honey-bees this is not the case. 



Merritt (1897:4) found the floral structure as described by Mueller 

 (1883:261), except that she noted no lengthening of the style as the flower 

 expanded. The style seemed unduly long, to such an extent that the lobes 

 were often so high that the bee missed them. Only 1 honey-bee in 5 touched 

 a stigma. Honey-bees and Osmia californica were the chief visitors. 

 Knuth (1906:441) records a number of variations in the flower mechanism, 

 and gives lists that show this to be primarily an apid flower. 



EXPERIMENTS. 



CHANGE OF POSITION. 



Racemes inverted. — When the flower-stalk of Chamaenerium is in- 

 verted, the parts are reversed with respect to the position in which the 

 bee is accustomed to find them. The style and the stamens now project 

 upward, leaving only the petals and sepals of the lower half of the flower 

 as a place to land. These often project backward in a such a way that it is 

 difficult for an insect to stay on them. Three individuals of Bombus juxtus 

 went to inverted flowers at different times and tried to discover the nectar, 

 but flew away without finding it. In another experiment wet cotton was 

 tied over the cut end of three racemes to keep the flowers from wilting, and 

 each one inverted was fastened alongside a normal cluster. Table 34 

 gives the results of an hour's observation on two different days, an equal 

 number of normal and inverted flowers being used in each case. 



Table 34. — Visitors and visits to normal and inverted racemes. 



In the first experiment as many individuals of Bombus juxtus visited 



inverted as normal stalks, but the number of flowers visited was only half as 



great. In the second, the visitors to the changed clusters were four times 



as numerous and the number of flowers visited almost 10 times as great. 



However, this was due largely to the presence of the horizontal racemes, 



the visitors and visits to the inverted ones being much the same for the 



two cases. 



MUTILATION. 



Floral envelopes removed. — This mutilation makes the whole raceme 

 much less conspicuous even than when in bud, and gives it a pale, feathery 

 appearance not at all like the normal one. The 24 mutilated stalks were 

 4 feet away from those bearing normal flowers (plate 17). 



