Page:Popular Science Monthly Volume 43.djvu/231

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219
ADAPTATIONS OF SEEDS AND FRUITS.

Winds which would break them off are effectually resisted by their strong yet flexible footstalks; and possible injury by bruising is averted by tough, elastic walls, often cushioned by prickles or other appendages.

Sudden changes of temperature, before they can penetrate to the unripe seeds, are rendered harmless by the blanketing effect of pulp or other material.

For protection from the animal world, immature fruits have developed a number of interesting devices. Almost universally "green" fruits so harmonize with surrounding color as readily to escape detection. In fact, the hazelnut is enveloped in a leafy coat which renders it very inconspicuous. The nutritious albumen of the seed is often fortified by such impenetrable shells as those of the cocoanut and others. Perhaps there is a formidable armament of prickles, as in the chestnut; or of stinging hairs, as is the case with some pods. Characteristic of immature fruits are disagreeable taste and consistence. Compare an unripe peach, sour and stringy, with the same fruit in its luscious maturity.

But all these contrivances fail to repel certain enemies of growing fruits. The apple's inconspicuousness, toughness, and sourness are of little avail against the young progeny of the genus Homo.

In many remarkable instances plants by their movements are able to protect their precious seeds from injury. In our common fall dandelion the whole flower closes up while the seeds are ripening, but reopens at their maturity. Furthermore, the upright flower stalk sinks to the ground when the flowers fade, but erects itself again when the seeds are ready to be scattered by the wind. In one of our winter house plants, the common cyclamen, the flower stalk coils up after flowering, bringing the pod to the ground to ripen; and our sweet white water lily, after expanding and withering above water, sinks to mature its seeds in safety. Other more remarkable but less common cases might be cited to show the extreme care with which plants preserve their seeds from possible destruction.

At maturity the one object of the seed is to secure the advantages of wide dispersion, and to effect this purpose Nature uses all means at hand. The agencies against which she so lately contrived are now most sedulously sought, and almost endless are the modifications of structure which enable seeds to spread far and wide.

"Dehiscence," the splitting open of a ripe pod, is manifestly a provision for seed dispersion. In its simplest form dehiscence merely exposes seeds to various conveying agencies: to the wind, in the milkweed; to birds, in the case of some brightly colored beans. Other plants, however, do more than this. Our wild