Page:Popular Science Monthly Volume 5.djvu/151

Rh the varying insect, or die out. And we have no right to assume that the body of an insect is a fixed bulk or structure any more than that the "instinct" or intelligence is fixed and invariable. Prof. Riley has shown the extreme probability that the peculiar modification of the palpus of the female yuccasella, which makes her the marriage-priestess of the yucca, was brought about little by little, as the peculiar structure of the flower came little by little. Flowers must vary with insects, and insects with flowers—yucca with yuccasella, and yuccasella with yucca—or both must die.

We have now the rationale of colors and odors. As vitality seems to have some general relation to color, perhaps the first show of color in a floral envelope was due to a slight diminution of vital force. Color being advantageous to the plant by attracting insects, when once it appeared its shades would be multiplied and intensified age after age, by natural selection. And as color is developed little by little as the result of insect-vision, modifications of structure are developed, in equal pace, by insect-touch.

This is not all. An organism is modified by all which environs it. Mr. Spencer, in his great work on "Biology," has shown us that the form of the cell, the leaf, the branch, the trunk, the flower, is determined in great part by the environment. Varying amounts of sunshine or shade modify the form of a branch. A prevailing wind modifies the form of a tree. A change of position on the stem changes the form of a flower. The drooping gloxinia in your conservatory is bi-symmetrical, and has a rudimental fifth stamen. Culture brings the flower up, erect on the stem, makes it radically symmetrical, restores the rudiment to a perfect stamen, prunes the flower of its eccentricities, and makes it regular—just as it does with a man.

Nature is, in the plant, what her name implies, "natura," a something about to be, a continual becoming. We see what changes are going on in the garden. Changes the same in kind are going on in the fields and the woods. A stroll over Goat Island on any May day will show the observant eye how variable in size and color and even in structure is the Trillium grandiflorum. The white-weed which overruns our Eastern meadows has sported into a score of incipient