Page:Popular Science Monthly Volume 25.djvu/452

438 boys, it probably despairs—it has acquired a comparatively hard and woody shell, surrounded by a bitter and acrid husk. But its ally, the bitter-nut, has hit accidentally upon a still more excellent and cunning device: it has made the actual seed itself, the menaced kernel, a reservoir for its disagreeable bitter juice. Consequently, it needs much less external protection than the hickory, and every American boy knows well that its shell can be much more readily and easily broken than that of its sweeter relations. Why hickory-nuts should be less protected than butternuts, on the other hand, is a more difficult question; I incline to believe it is because of the greater number produced by each tree annually, so that, in spite of all the havoc wrought by squirrels and other depredators, enough must always have remained and sprouted to keep up the full normal number of the species from one generation to another.

Almost all nuts follow more or less one of these two protective types—the type of the hickory and the type of the bitter-nut—or even sometimes both together. In the tropics, where forestine animals are most developed, the nuts often reach a very high stage of evolution. The cocoanut is a familiar example: it has a soft outer husk, stringy and loose, which breaks and deadens its fall from the tall and graceful palm-trees on which it grows; and inside this yielding, protective mat-work, it has a very solid shell, inclosing the large and richly-stored kernel. But the cashew-nut is, perhaps, the most remarkable in some respects of any known example. It has taken most extraordinary pains to preserve its kernel from injury; and it has done so by a curious combination of the tactics peculiar to attractive fruits with those peculiar to repellent nuts. Its stalk swells out into a fleshy edible tuber, something like a pear in shape, and endowed with all the usual allurements of bright color and sweet taste. By this bribe, it entices the South American monkeys to pick and aid in dispersing its seed. But, at the same time, it carefully wraps up the nut itself in an acrid, pungent covering, and places it at the outer end of the pear-like stalk. Woe betide the adventurous monkey who tries to eat the inner kernel of this decidedly well-protected nut! The pungent juice of the rind not only burns his tongue and lips, but even removes the skin from his mischievous fingers as effectually as it could be removed by a cantharides-plaster. Hardly less quaint are the tactics adopted by the familiar pea-nut of our childhood, which is really the underground pod of a bean-like plant. This secretive vegetable has hit upon the device of producing its seeds on subterranean branches, and so escaping the notice of most open-air birds and mammals; though, in thus cunningly avoiding the Scylla of the upper earth, it has merely fallen against the Charybdis of grubbing pigs and burrowing rodents. The little English subterranean clover—I forget just now whether it grows in America, too, and Dr. Asa Gray's magnificent work is not at hand—has an even stranger plan for escaping from the sheep, on whose