The pollen of flowers is a most fine, delicate dust. It must be conveyed without injury in the most delicate manner. Many flowers are exceedingly high up, as on climbing vines, or growing on tree-tops, peaks, or house-tops. Many other plants are very low down, lying close to the ground, as the bluets, chickweed, arbutus, partridge-berry, and others. A large number of plants are in positions inaccessible to man or the larger animals. Man excepted, the larger animals seem generally to have a destructive mission to plants, devouring, breaking, or trampling down. Men themselves are often ruthless destroyers of beautiful plants, and seem to care for and conserve only what concerns human convenience. Here, then, we have the problem of plants fixed in their places, needing carriers for their pollen to distant plants of their own kind, at the exact period of maturity. The carriers must be able to go high or low, into all manner of different localities; they must be delicately made, so that they will not injure the plants which they visit, capable of carrying the frail pollen grains unharmed, and they must have some object of their own in these visitations, which shall infallibly secure their doing of the work required. Finally, let us remember that the pollen of flowers is but seldom spread where it is easy to secure it. The buttercup lavishly expends a golden saucer of pollen; the lily has a wide-open door, near which hangs the antlers, like so many ready bells. On the other hand, how long and narrow are the throats of the morning-glories and honeysuckles; how tiny are the tubes of mint, thyme, and clover; how fast-closed is the mouth of the snap-dragon; how narrow the fox-glove’s throat. Pollen-carriers must be able to secure the dust so jealously kept, and must be afforded a reward for their trouble. What form of animal life meets all these conditions? But one--the insect. It is generally light and delicate in structure, active, winged; its life is conterminous with that of flowers; they are spring and summer guests. The slender shape and the long, slim mouth organs of the insect can penetrate and gently force open flower tubes and the fast-shut lips of corollas; the velvet coats and fine, waving antennæ will receive and carry uninjured the precious dust, and the insect habit of constant roaming from bloom to bloom assures the accomplishment of its important errand. Not all insects, but a few widely-distributed families, are the chosen partners of the flowers; these are the various tribes of bees, moths, and butterflies, with some help from a few others. “Nothing for nothing” seems to be a law of nature. What does the flower offer to the insect for its services as pollen distributer? Honey, which is the chief food of flying insects, also wax, and pollen for its private use at home. The miller, we know, takes toll from the flour he grinds.