IV 
OUTLINES OF 
are then often distinguished as adventitious, and this term is by some applied to all 
roots which are not in prolongation of the original radical. 
20. Roots are 
fibrous , when they consist chiefly of slender fibres. 
tuberous , when either the main root or its branches are'thickened into one or 
more short fleshy or woody masses called tubers (25) . 
taproots, when the main root descends perpendicularly into the earth, emitting 
only very small fibrous branches. 
21. The stock of a herbaceous perennial, or the lower part of the stem of an 
annual or perennial, or the lowest branches of a plant, are sometimes underground 
and assume the appearance of root. They then take the name of rhizome. The 
rhizome may always be distinguished from the true root by the presence or pro- 
duction of one or more buds, or leaves, or scales. 
§ 3. The Stock. 
22. The Stock of a herbaceous perennial, in its most complete state, includes a 
small portion of the summits of the previous year’s roots, as well as of the base of 
the previous year’s stems. Such stocks will increase yearly so as at length to form 
dense tufts. They will often preserve through the winter a few leaves, amongst 
which are placed the buds, which grow out into stems the following year, whilst the 
under side 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 the texture, usually less woody. 
23. In some perennials, however, the stock consists merely of a branch, which 
proceeds in autumn from the base of the stem either aboveground or underground, 
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, even the branch on which these buds were formed, has died away. 
These annual stocks, called sometimes hybernacula, offsets, or stolons, keep up the 
communication between the annual stem and root of one year and those of the 
following year, thus forming altogether a perennial plant. 
24. The stock, whether annual or perennial, is often entirely underground or root- 
like. This is the rootstock , to which some botanists limit the meaning of the term 
rhizome. When the stock is entirely root-like, it is popularly called the crown of 
the root. 
25. The term tuber is applied to a short, thick, more or less succulent rootstock 
or rhizome, as well as to a root of that shape (20), although some botanists propose 
to restrict its meaning to the one or to the other. An Orchis tuber, called by some 
a knob, is an annual tuberous rootstock with one bud at the top. A potato is an 
annual tuberous rootstock with several buds. 
26. A bulb is a stock of a shape approaching to globular, usually rather conical 
above and flattened underneath, in which the bud or buds are concealed, or nearly 
so, under scales. These scales are the more or less thickened bases of the decayed 
leaves of the preceding year, or of the undeveloped leaves of the future year, or 
both. Bulbs are annual or perennial, usually underground or close to the ground, 
but occasionally buds in the axils of the upper leaves become transformed into 
bulbs. Bulbs are said to be scaly when their scales are thick and loosely imbricated, 
tunicated when the scales are thinner, broader, and closely rolled round each other 
in concentric layers. 
27. A corm is a tuberous rootstock, usually annual, shaped like a bulb, but in 
which the bud or buds are not covered by scales, or of which the scales are very 
thin and membranous. 
§ 4. The Stem. 
28. Stems are 
erect, when they ascend perpendicularly from the root or stock; twiggy or 
virgate, when at the same time they are slender, stiff, and scarcely branched. 
sarmentose, when the branches of a woody stem are long and weak, although 
scarcely climbing, 
