BEES AND FLOWERS. 237 
and sticky yet, and so it does not use the pollen- 
grains. 
Now suppose that a bee comes to the flower. The 
honey she has to fetch lies inside the tube at h, and 
the one stamen being loose she is able to get her 
proboscis in. But if she is to be of any use to the 
flower she must uncover the pollen-dust. See how 
cunningly the flower has contrived this. In order to 
put her head into the tube the bee must stand upon 
the wings w, and her weight bends them down. But 
they are locked to the keel k by the knob fitting in 
the hole d, and so the keel is pushed down too, and 
the sticky pollen-dust is uncovered and comes right 
against the stomach of the bee and sticks there ! As 
soon as she has done feeding and flies away, up go 
the wings and the keel with them, covering up any 
pollen that remains ready for next time. Then when 
the bee goes to another flower, as she touches the 
stigma as well as the pollen, she leaves some of the 
foreign dust upon it, and the flower uses that rather 
than its own, because it is better for its seeds. If 
however no bee happens to come to one of these 
flowers, after a time the stigma becomes sticky and it 
uses its own pollen : and this is perhaps one reason 
why the bird's-foot trefoil is so very common, because 
it can do its own work if the bee does not help it. 
Now we come lastly to the Orchis flower.* Mr. 
Darwin has written a whole book on the many curi- 
ous and wonderful ways in which orchids tempt bees 
and other insects to fertilize them. We can only take 
the simplest, but I think you will say that even this 
* The nearest species for study in America are the Habenarias. 
