Leaves as Food.—Grazing animals feed almost entirely on tender shoots or leaves, blades of grass, and other herbage. Certain leaves and buds are used by man as food. Lettuce, beet tops, kale, spinach, broccoli, are examples. A cabbage head is nothing but a big bud which has been cultivated by man. An onion is a compact budlike mass of thickened leaves which contain stored food.
Stems used as food.
Stems as Food.—A city child would, if asked to name some stem used as food, probably mention asparagus. We sometimes forget that one of our greatest necessities, cane sugar, comes from the stem of sugar cane. Over seventy pounds of sugar is used each year by every person in the United States. To supply the growing demand beets are now being raised for their sugar in many parts of the world, so that nearly half the total supply of sugar comes from this source. Maple sugar is a well-known commodity which is obtained by boiling the sap of sugar maple until it crystallizes. Over 16,000 tons of maple sugar is obtained every spring, Vermont producing about 40 per cent of the total output. The sago palm is another stem which supports the life of many natives in Africa. Another stem, living underground, forms one of man's staple articles of diet. This is the potato.
Roots as Food.—Roots which store food for plants form important parts of man's vegetable diet. Beets, radishes, carrots, parsnips, sweet potatoes, and many others might be mentioned.
The following table shows the proportion of foods in some of the commoner roots and stems:—
| Water | Proteins | Carbohydrates | Fat | Mineral Matter | |
|---|---|---|---|---|---|
| Potato | 75.0 | 1.2 | 18.0 | 0.3 | 1.0 |
| Carrot | 89.0 | 0.5 | 5.0 | 0.2 | 1.0 |
| Parsnip | 81.0 | 1.2 | 8.7 | 1.5 | 1.0 |
| Turnip | 92.8 | 0.5 | 4.0 | 0.1 | 0.8 |
| Onion | 91.0 | 1.5 | 4.8 | 0.2 | 0.5 |
| Sweet potato | 74.0 | 1.5 | 20.2 | 0.1 | 1.5 |
| Beet | 82.2 | 0.4 | 13.4 | 0.1 | 0.9 |
Seeds and fruits used for food.
Fruits and Seeds as Foods.—Our cereal crops, corn, wheat, etc., have played a very great part in the civilization of man and are now of so much importance to him as food products that bread made from flour from the wheat has been called the "staff of life." Our grains are the cultivated progeny of wild grasses. Domestication of plants and animals marks epochs in the advance of civilization. The man of the stone age hunted wild beasts for food, and lived like one of them in a cave or wherever he happened to be; he was a nomad, a wanderer, with no fixed home. He may have discovered that wild roots or grains were good to eat; perhaps he stored some away for future use. Then came the idea of growing things at home instead of digging or gathering the wild fruits from the forest and plain. The tribes which first cultivated the soil made a great step in advance, for they had as a result a fixed place for habitation. The cultivation of grains and cereals gave them a store of food which could be used at times when other food was scarce. The word "cereal" (derived from Ceres, the Roman Goddess of Agriculture) shows the importance of this crop to Roman civilization. From earliest times the growing of grain and the progress of civilization have gone hand in hand. As nations have advanced in power, their dependence upon the cereal crops has been greater and greater.