INTRONUCTORY LESSONS, xy 
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trees and most other plants are exogens. Palm-trees, Century-plants, 
grasses, and the ‘‘small grains,” are endogens. 
Herbs are plants whose stems die, at least to the ground, after 
they have blossomed and matured fruit. These are Annuals when their 
lives are limited to one season; Biennials when they die the second year 
—not producing fruit the first year; Perennials when they live on year 
after year, their stems dying annually down to the ground. The under- 
ground portions of such stems are called— 
Rootstocks. This name applies more particularly to such stems as 
grow nearly horizontally under ground, or become thick and fleshy with 
nutritious matter, which enables the plant to make rapid first growths 
each year. A rootstock can usually be distinguished from a true root 
by its bearing buds. 
Bulbs are formed by a peculiar bud growth in which the leaves or 
their bases become very thick and fleshy, with a store of nourishment, 
while the stem grows in diameter, but scarcely at all in length. 
Coated or Tunicated Bulbs are those in which the leaves form a 
succession of envelopes, as in the onion. If the leaves or leaf-bases are 
narrow, as in the lily, the bulb is Scaly. 
Corms resemble bulbs, but are solid, and have more the nature of 
Tubers, which are the thickened ends of slender, branching, under- 
ground stems, as potatoes, ground artichokes, etc. 
Leaves. Collect the leafy stems of many kinds of plants. Ob- 
serve the arrangement of the leaves on the stems. A few like Erodium 
(Filaria), the Catchfly, Pink, Fuchsia, Mint, etc., have Opposite leaves. 
Possibly you may find a Collinsia, or stem of Cleavers, with the leaves ia 
Whorls of three or more. Most plants have Alternate leaves. You will 
find some plants like Plantain, with a bunch of leaves growing from the 
ground, but no leafy stems. Such leaves come from rootstocks, and are 
said to be Radical. Plantain, Dodecatheon, Primrose, etc. have the leaves 
all radical. Many perennial herbs have radical leaves, as well as ordi- 
nary stem leaves, and, these usually differ more or less from the stem 
leaves. 
Observe that stems and branches end in buds or flowers, and that 
