Page:Popular Science Monthly Volume 13.djvu/625

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THE ORIGIN OF FRUITS.

our own case, the long habituation of our frugivorous ancestors to this particular stimulant has rendered us peculiarly sensitive to its effects. But even from the first, there can be little doubt that a body so specially fitted to arouse sensation in the gustatory nerve must have afforded pleasure to the unspecialized palates of birds and rodents: for we know that even in the case of naturally carnivorous animals, like dogs, a taste for sugar is extremely noticeable. So, then, the sweet juices of the fruit were early added to its soft and nutritive pulp as an extra attraction for the animal senses.

Perfume, of course, follows in the wake of sweetness. Indeed, the difference between taste and smell is much smaller than most people imagine. When tiny floating particles of a body, in the gaseous state, affect certain exposed nerves in the cavity of the nose, we call the resulting sensation an odor; when larger particles of the same body, in the liquid or dissolved state, affect similar exposed nerves in the tongue, we call the resulting; sensation a taste. But the mechanism of the two senses is probably quite similar, while their exciting causes and their likes or dislikes are almost identical. As our great psychological teacher, Mr. Herbert Spencer, well puts it, "smell is anticipatory taste." So we need not be surprised to find that the delicate fragrance of peaches, strawberries, oranges, and pineapples, is a guide to their edibility, and a foreshadowing of their delicious flavor, leading us on by an instinctive action to place the savory morsels between our lips.

But the greatest need of all, if the plant would succeed in enticing the friendly parrot or the obsequious lemur to disperse its seed, is that of conspicuousness. Let the fruit be ever so luscious and ever so laden with sweet sirups, it can never secure the suffrages of the higher animals if it lies hidden beneath a mass of green foliage, or clothes itself in the quiet garb of the retiring nut. To attract from a distance the eyes of wandering birds or mammals, it must dress itself up in a gorgeous livery of crimson, scarlet, and orange. The contrast between nuts and fruits is exactly parallel to the contrast between the wind fertilized and the insect-fertilized flowers. An apple-tree laden with its red-cheeked burden, an orange-bough weighed down with its golden spheres, a rowan or a holly-bush displaying ostentatiously its brilliant berries to the birds of the air, is a second edition of the roses, the rhododendrons, and the May-thorns, which spread their bright petals in the spring before the fascinated eyes of bees and butterflies. Some gay and striking tint, which may contrast strongly with the green foliage around, is needed by the developing fruit, or else its pulpiness, its sweetness, and its fragrance, will stand it in poor stead beside its bright-hued compeers.

How fruits began to acquire these brilliant tints is not difficult to see. We found already in the case of flowers that all external portions of a plant, except such green parts as are actually engaged in assimi-