But this was not good for the plant. Those flowers that in some way became fertilized by pollen from other plants of the same variety, by cross-fertilization, in fact, were healthier and stronger than those fertilized by their own pollen. In such plants as wind-blown pollen reached this cross-fertilization was an easy matter, but the buttercup is not one of these. It is forced to rely upon insects for fertilization.So the plant began to secrete a sweet drop at the base of each green petal. Such insects as discovered this nectar and stopped to sip were dusted with the pollen of the plant and carried it to other flowers, where it fertilized the pistils, the insect gathering from every blossom a fresh burden of pollen to be carried along on his nectar-seeking round. This was very good, so far as it went, but the flowers were pale and inconspicuous, and many of them, overlooked by the insects, were never visited. Certain ones, however, owing to accidents or conditions of soil and moisture, had the calyx a little larger, or brighter colored than their fellows, and these the insects found. It happened, therefore, if anything ever does merely happen, that the flowers with bright petals were fertilized, and their descendants were even brighter colored. Thus, in time, the buttercup, by the process which, for lack of a better name, we call natural selection, came to have bright yellow petals, because these attract the insect best adapted to fertilize itIf man’s æsthetic sense is gratified by the flower’s beauty, why man is by so much the better off, but that man is pleased by the bright color is not half so important to the buttercup as is the pleasure of a certain little winged beetle which sees the shining golden cup and knows thatit means honeyIn the same way the lupin, yonder, with its pretty blue and white blossoms, has developed its blue petals because it is fertilized by the bees. They seek it as they do other blossoms, not only for honey, but for the pollen itself, which stands them in place of breadThe very shape of the flower is due to the visits of countless generations of this insect. The bee is the insect best adapted to fertilize the lupin, and when he alights upon the threshold of a blossom his weight draws the lower petal down, and entering to suck the sweets he gets his head dusted with pollen. If a fly were to gain entrance to the flower, he would carry away no pollen. He is smaller than the bee, and his head could not reach it. So honey-seeking flies alight in vain; their weight is not enough to press the calyx open, so they may not enter and drink of its sweets. Yonder on a blossom of the mimulus, the odd-looking monkey-plant, a honeybee just had this same experience. The bumblebee is the only insect that is large enough to reach the pollen in this blossom, and so its doors will open only to him. Botanists tell us that all this great family, to which belong the various peas blossoms and their cousins, were once five-petaled plants, but natural selection has brought about their present shape, which is an admirableprotection against the depredations of small insects that could only rob but could not fertilize the flowers
Blue is the favorite color of the honeybee, and next to blue he prefers red. So bee blossoms are blue or red.