Page:Popular Science Monthly Volume 13.djvu/620

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depending wholly upon the stock of nutriment laid up for it in the corm.

If we look at the parts of plants which are used as food by man of other mammals, we shall see even more clearly the community of nature between the animal functions and those of seeds, flowers, and bulbs. It is true that the graminivorous animals, like deer, sheep, cows, and horses, live mainly off the green leaves of grasses and creeping plants. But we know how small an amount of food they manage to extract from these fibrous masses, and how constantly their whole existence is devoted to the monotonous and imperative task of grazing for very life. Those animals, however, who have learned to live at the least cost to themselves always choose the portions of a plant which it has stored with nourishment for itself or its offspring. Men and monkeys feed naturally off fruits, seeds, and bulbs. Wheat, maize, rye, barley, oats, rice, millet, peas, vetches, and other grains or pulses, form the staple sustenance of half mankind. Other fruits largely employed for food are plantains, bananas, bread-fruit, dates, cocoanuts, chestnuts, mangoes, mangostines, and papaws. Among roots, tubers, and bulbs, stored with edible materials, may be mentioned beets, carrots, radishes, turnips, swedes, ginger, potatoes, yam, cassava, onions, and Jerusalem artichokes. But if we look at the other vegetables used as food, we shall observe at once that they are few in number, and unimportant in economical value. In cabbages, Brussels sprouts, lettuce, succory, spinach, and water-cress, we eat the green leaves; yet nobody would ever dream of making a meal off any of these poor food-stuffs. The stalk or young sprout forms the culinary portion of asparagus, celery, seakale, rhubarb, and angelica, none of which vegetables are remarkable for their nutritious properties. In all the remaining food-plants, some part of the flowering apparatus supplies the table, as in true artichokes, where we eat the receptacle, richly stocked with nutriment for the opening florets; or in cauliflower, where we choose the young flower-buds themselves. In short, we find that men and the higher animals generally support themselves upon those parts of plants in which energy has been accumulated either for the future growth and unfolding of the plant itself, or for the sustenance of its tender offspring.

And now, after this long preamble, let us come back to our original question, and seek to discover what is the origin of fruits.

In botanical language, every structure which contains the seeds resulting from the fertilization of a single blossom is known as a fruit, however hard, dry, and unattractive, may be its texture or appearance. But I propose at present to restrict the term to its ordinary meaning in the mouths of every-day speakers, and to understand by it some kind of succulent seed-covering, capable of being used as food by man or other vertebrates. And our present object must be simply to discover how these particular coverings came to be developed in the slow course of organic evolution,