4 BULLETIN 123, U. S. DEPARTMENT OF AGRICULTURE. 
important groups under such a classification would be that which 
includes the roots or similar underground parts. To the botanist, 
there are important differences between such forms as true roots 
like sweet potatoes or parsnips, tubers like white potatoes and 
Jerusalem artichokes, root stalks or rhizomes like ginger, bulbs like 
onions, etc., but from the point of view of human food they may all 
be roughly classed together as root crops. They represent the store 
of nutritive material which the plant collects underground to draw 
on during its growth. Asparagus represents the use of stems as food. 
Sago, which is made from the pith of a species of palm, is an example 
of the use of a part of a tree trunk. In celery and rhubarb the leaf- 
stalks are the edible portion. Many kinds of leaves are used, both 
dried and fresh. Among the fresh ones may be mentioned lettuce, 
endives, spinach, and greens of various kinds. Dried leaves appear 
in tea and such flavoring matters as sage, thyme, bay, etc. Fewer 
flowers are used than most other plant forms. Cauliflower and 
globe or French artichokes, however, represent the undeveloped 
fiower heads, while capers are pickled flower buds and cloves are 
dried ones. There is a great variety in the fruits and seeds used. 
Sometimes the preparations of cereal grains, such as hulled corn or 
hominy, rice, or macaroni and other pastes made of wheat flour, are 
served with meat like potatoes. Another important group consists 
of various members of the pulse family. Most important of these 
are peas and beans, some of which are eaten half ripe in their pods, 
some ripe and fresh, and some dried. Tomatoes, eggplants, and 
various members of the gourd family, such as squash, pumpkins, 
cucumbers, etc., are still other fruit forms used as vegetables. The 
seeds of mustard, celery, nutmeg, allspice, cassia, and various peppers 
are dried and used for flavoring. 
THE COMPOSITION OF PLANTS. 
Every plant may be considered a factory into which are carried 
substances from the air and the earth to be manufactured into other 
and very different products. In general, the processes which go on 
within the plants are those of upbuilding, the substances which en- 
ter being simple and those which are produced complex. : 
Some plants may be considered factories for the manufacture of 
food, others for textile fibers, and still others for fuel or building 
materials. Some serve several or all of these purposes. But what- 
ever the use to which the plants are put, they all have certain com- 
mon characteristics which may be learned from any work on botany. 
Most foods include more or less refuse as well as the edible por- 
tion. Modern commercial enterprise separates much of the refuse 
before delivering foods to the consumer. In each lesson notice the 
small portion of the plant studied which is actually used as food. 
