150 BRITISH PLANTS 
3. Storage of Food in Subterranean Organs—(a) Tubers. 
—(i.) Stem-tubers—e.g., potato, Jerusalem artichoke. 
(ii.) Root-tubers—e.g., sweet potato. 
(6) Rhizomes—e.g., ginger, arrowroot. 
(c) Fleshy Roots.—(i.) Of biennials—e.g., carrot, tur- 
nip, parsnip, swede, mangold, radish, beet. 
(ii.) Of perennials—e.g., Manihot utilissima, the man- 
dioc, from which tapioca is obtained. 
(dz) Bulbs—e.g., onion—the leaves of which are full of 
sugar. 
4. Edible Aerial Organs, yielding most of our table 
vegetables. 
(a) Stems.—(i.) Sugary pith—e.g., sugar-cane. Maple- 
sugar is obtained by boring holes in the stem of the sugar- 
maple, a native of North America, when the sap is setting 
towards the opening buds in spring. 
(ii.) Starchy pith—e.g., the sago-palms—from which 
sago is obtained. 
(b) Leaves—e.g., cabbage, lettuce, spinach. 
(c) Buds —e.g., brussels- sprouts, from a variety of 
cabbage. 
(d) Young Shoots—e.g., asparagus. 
(e) Petioles—e.g., celery, rhubarb. 
(f) Inflorescences—e.g., cauliflower, broccoli. 
5. Seedlings (e.g., mustard and cress). 
Fodder-Plants.—Animals, in the main, eat the same 
vegetable food as man. Most of our domestic animals 
are vegetable feeders, and in these the digestive organs 
are adapted to the consumption of large quantities of 
raw vegetation—e.g., horse, cow, sheep, goat. Fodder- 
plants for grazing animals include grasses, leguminous 
herbs, and root-crops. 
Economic Botany is the study of plants from the point 
of view of their utility to man. We have already dealt 
with the most important side of the subject—human food. 
But plants have many other uses to man besides nutrition. 
They offer to him material by means of which countless 
needs are satisfied and many activities served. From 
the vegetable world is drawn a large part of the raw 
material which is used in the preparation of industrial 
products—cotton, flax, hemp, jute, oils, varnishes, rubber, 
dyes, and timber. Vegetable products constitute a large 
and often dominant source of wealth in every country. 
