INTRODUCTION TO BOTANY. lil 
winter a few leaves, amongst which are placed the buds, which grow out 
into stems the following year, whilst the underside of the stock emits new 
roots from or amongst the remains of the old ones. These perennial stocks 
only differ from the permanent base of an undershrub in the shortness of 
the perennial part of the stems, and in their usually less woody texture. 
17. In some perennials the stock consists merely of a branch, which 
issues in autumn from the base of the stem, either above-ground or under- 
ground, and produces one or more buds. This branch, or a portion of it, 
alone survives the winter. In the following year its buds produce the new 
stem and roots, whilst the rest of the plant has died away. These annual 
stocks, called sometimes hybernacula, offsets, or stoles, keep up the communica- 
tion between the annual stem and root of one year and those of the following 
year, thus forming altogether a perennial plant. 
18. The stock, whether annual or perennial, is often entirely under- 
ground, or root-like. To this some botanists limit the terms rootstock or 
rhizome. 
19. The term tuber is applied to a short, thick, succulent rootstock, as 
well as to a root (15) of that shape. The tuber of an orchis, by some called 
a knob, is an annual tuberous rootstock with one budatthetop. A potato 
is an annual tuberous rootstock with several buds. 
20. A bulb is a subglobose or conical rootstock, formed chiefly of the 
fleshy bases of the preceding year, or of the undeveloped leaves of the fu- 
ture year, or of both; it emits roots from its base, and a stem and foliage from 
its centre, and frequently forms dzzd/ets or offsets in the axils of its scales. 
21. Bulbs are, : 
scaly, when their scales are thick, narrow, and loosely imbricated, 
as in the white Lily ; 
tunicated, when the scales are thin, broad, and closely rolled round 
in concentric layers, as in the Onion. 
22. A corm is a fleshy, starchy, and solid rootstock, shaped like a bulb, 
but not scaly, though often coated with the membranous leaf-bases of a 
previous season; its buds are naked, and small in comparison to the fleshy 
base from which they spring. The Ixias, Gladioluses, etc., afford examples 
of this form of rootstock. 
§ 4. The Stem. 
23. The Stem grows upwards from the root, bears buds which grow out 
into leafy branches, and finally produces flowers and fruit. 
24. Stems are, 
erect, when they spring perpendicularly from the root or stock ; 
decumbent, or ascending, when they spread nearly horizontally at the 
base, and then gradually turn upwards and become erect ; 
procumbent, when they spread along the ground for the whole or the 
greater portion of their length ; 
prostrate, when they lie still closer to the ground ; 
creeping, when they emit roots at their joints. This term is also 
applied to rhizomes or reots, when they spread horizontally. 
tufted (cespitose), when short, and growing in thick, cushion-like 
tufts. 
diffuse, when spreading loosely without being strictly decumbent or 
procumbent. 
25. Weak stems are said to twine when they support themselves by 
winding spirally round any object ; and to climb when they support them- 
selves by their leaves, or by special clasping organs called tendrils, which 
are usually either imperfectly formed leafstalks or flowerstalks. Twining 
stems are sometimes called voluble. Sarmentose stems or branches are woody, 
long, and weak, 
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