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As soon as the insect has withdrawn from the 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] 
