ON VARIATION 



and snugly hugs the spadix, so that the fly, buzzing 

 about in the chamber below, becomes thoroughly 

 covered with the pollen dust. 



This done, the flower slowly unfolds and 

 permits the pollen laden insect to escape. 

 ***** 



Many other flowers show equal or greater 

 ingenuity. 



In some varieties of the sage, the pollen-bear- 

 ing stamens actually descend and quickly rub the 

 yellow dust on either side of the insect, after which 

 they fall back into their former position above the 

 nectar cells. 



Most of the orchids, too, show an unusual 

 ingenuity. 



One species bears its pollen in small bundles, 

 the base of each bundle being a sticky disc. The 

 structural arrangement of the flower is such that 

 the insect cannot secure its nectar without carrying 

 away at least one of the bundles. A pollen bundle 

 glues itself to the head of the insect and curves 

 upward like a horn. 



As soon as the insect has withdrawn from the 

 flower, this pollen horn bends downward in front 

 of the insect, close to its head, so that when the 

 next flower is entered the dust can hardly fail to 

 reach a receptive portion of the pistil. 



In this orchid there is but a single receptive 



[83] 



