on oxidation in order to live and grow, and must reproduce their kind in order to perpetuate the species. We turn now to a discussion of some of the uses of plants to man, and some of the ways in which they are injurious.

I. SOME OF THE USES OF PLANTS TO MAN

135. Uses of plants for food. By repeated experiments we have proved that various parts of plants contain generous stores of starch,

sugar, protein, and mineral matters. In our study of human biology we shall find that the foods which are essential for Our bodies are composed of these same substances. It is for this reason that man and other animals are SO largely dependent upon plants for food. As examples we may mention roots like parsnips, beets, and sweet potatoes; stems, like

common potatoes, asparagus, and sugar cane; leaves, such as cabbage and lettuce; flowers, for example, cauliflower;

fruits, like apples and peaches; and seeds and grains, like beans, wheat, and corn.

136. Suggestions for further study of plants used as food. Study No. 58. (Optional.) Visit a vegetable market, make a list of the various plant products sold for food, and arrange them in a table as follows:

Select one or more of the following topics for special study: wheat, corn, potatoes, oats, rice. Consult Bailey's " Cyclopedia of American Agriculture," Vol. II," Crops," any encyclopedia, or the publi

of

cations of the U.S. Department Agriculture. Determine (1) the parts of the United States (or of the world) in which the crop is raised in large quantity, (2) the amount and value of a year's crop, (3) methods of harvesting and preparing the crop for the market.

137. Uses of plants for flavoring extracts, beverages, and medicines. We saw in a previous section that many parts of plants are available for use as food by man. Because,

also, of the presence of various flavoring compounds in plants, the following products are valuable. For instance, vanilla extract is made from the vanilla bean, pepper from pepper berries, horse-radish from the root of the horse-radish plant, and ginger from an underground stem.

We are dependent, too, upon plants for many beverages. The coffee berry supplies us with coffee, tea leaves with tea, and from the pods

and seeds of the cocoa tree we obtain cocoa and chocolate. Grapes are used to make wines, from apples cider is prepared, and from grains of various. kinds other alcoholic liquors are produced. Quinine, the wellknown remedy for malaria, was formerly obtained from the bark of a tree known as cinchona, which grows in Peru. This medicine is now obtained almost exclusively from trees cul

tivated in India and other Eastern countries. The camphor tree furnishes camphor gum; from the juice of poppy fruits opium and morphine are obtained; whole plants like peppermint supply us with valuable medicines. In fact, enormous numbers of drugs are prepared from various parts of plants.

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138. Suggestions for further study of parts of plants used as drugs. Study No. 59. (Optional.)

Visit a drug store or consult an encyclopedia, e.g. Bailey's" Cyclopedia of American Agriculture," Vol. II, "Crops," and make a list of common drugs obtained from plants. Fill out in your note-book a table like the following:

139. Uses of plants for clothing. (Quoted from Bailey's "Cyclopedia of American Agriculture," Vol. II, "Crops.") "Fiber-producing plants are second only to food plants in agricultural importance. In continental United States, however, cotton, hemp, and flax are the only fiber plants cultivated commercially; and aside from cotton and hemp, most of the raw fibers used in our industries are imported."

"The cotton of commerce is the hair or fiber on seeds of plants belonging to the Mallow family. . . . The plants are mostly shrubby, more or less branching, and two to ten feet high. . . . The fruit consists of three- to five-celled 'bolls,' which open at maturity through the middle of the cells, each cell liberating seven to ten seeds covered with long fibers. The fiber is a tubular hairlike cell, 1 to 12 of an inch in diameter, somewhat flattened and spirally twisted. It is this latter characteristic which gives

the cotton its spinning qualities. . . .

Picking or gathering cotton in the fields is a heavy item o expense. It must be picked by hand, as no mechanical appliance for harvesting has yet been invented which gives satisfactory results in practical working. The amount of cotton that one person can pick in one day varies from one hundred to five hundred pounds,

depending on the skill of the picker. One man can very easily care for the cultivation of twenty acres of cotton, but it requires two to four pickers to harvest such a crop rapidly enough to pre