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336 ESSENTIALS OF BOTANY 
fruit, as in the so-called cardamom seeds, or the seed, as in 
mustard and flaxseed, is the medicinal part of the plant. 
Occasionally some secretion or excretion of the plant is of 
remedial value, as in the case of Canada balsam and gum 
arabic. Nearly seventy families of angiosperms are repre- 
sented in the official list of medical plants... Some fam- 
ilies have medicinal properties quite generally distributed 
throughout their species, while others have only one or a 
few species with curative properties. 
Medical botany is a subject on which many special works 
have been written, but this brief summing-up is all that 
can be given here. 
(3) FOODS FOR DOMESTIC ANIMALS 
412. Some of the grains, especially corn, oats, and bar- 
ley, are largely fed to domestic animals. Of the roots and 
tubers which are used for human food, beets, carrots, tur- 
nips, and potatoes are considerably fed to cattle, sheep, 
and hogs in some parts of the country. 
Many of the grasses constitute pasture for grazing ani- 
mals or are made into hay. Throughout a large part of the 
United States the hay crop is one of the most important 
of all to the farmer, and its annual value usually amounts 
to over $500,000,000. Alfalfa, several clovers, soy-beans, 
and cow-peas are some of the principal plants of the Pea 
family useful as horse and cattle food. 
Forage is prepared from such plants as red clover, alfalfa, 
and others, cut green and fed to horses and cattle. Corn- 
stalks, when nearly mature, are largely used in this way, 
and the stems and leaves cut up and allowed to ferment are 
1 The United States Pharmacopeia. 
