Page:Popular Science Monthly Volume 42.djvu/87

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started on his quest with shoes of swiftness, charmed sword, and invisible cloak, may well have been one of Nature's models. Many a time since, the invisible cloak has given the victory to her heroes. In the hand-to-hand battle of life, which is continually waging, many an animal escapes unscathed simply by being so like the objects among which it lives that only the keenest sight can distinguish between them. This is "protective coloring." Walking-sticks resemble twigs; alligators, floating logs; brown bitterns, the rocks among which they stand motionless watching for prey; gay birds-of-paradise are almost invisible among the branches of brilliantly blossomed trees. But the phenomenon is not confined to animals.

A remarkable thing about fruits is the great difference in color between the dry and fleshy kinds. It is hard to think of a conspicuous dry fruit in all our flora, yet they are far the most numerous; for, of the eight hundred and eighty-nine genera of flowering plants given in Gray's Manual, eight hundred and nine have dry fruits. But many of the eighty fleshy-fruited genera are brightly colored: ten have white, eight yellow, eight yellowish, thirteen blue, twenty-three (usually shining) black, sixteen purple, twenty-five red species. Only four have no other color than green.

Surely this is a significant contrast. There is no intrinsic reason why a nut-shell should not be as brightly tinted as a peach skin, but in the light of modern theories of distribution the problem is simplified. It is now known that dry fruits are disseminated by purely mechanical means, by the agencies of wind and water, or by the unconscious help of animals to whose hair, feathers, or feet they adhere. But fleshy fruits are largely, often entirely, dependent upon animals which eat the attractive and palatable covering, and in one way or another scatter the uninjured seeds. As there are wind, water, and insect pollinated flowers, so there are wind, water, and animal carried fruits; and the first two classes of both are inconspicuous, the third commonly beautifully adorned. The negative reason, then, for the absence of color among dry fruits is the needlessness of attractive characters; but there is a positive and perhaps as powerful a cause which has operated to the same end. Dry fruits are by no means unpalatable. The staple vegetable foods, sought after alike by the lower animals and by man, are grains, legumes, and nuts. In their great popularity is their great danger; their treasure must be hidden. The seeds of many Compositæ, greedily eaten by birds, are therefore covered; the distasteful or even poisonous fruits of the parsley family freely exposed. The hard shells of nuts, the hairy or bristly coverings of many pods, defeat the attacks of numerous foes. But the charmed bodies of Siegfried and Achilles