TNTRODUCTION TO BOTANY. Ill 



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 fi-om or amongst the remains of the old ones. These im-ennial stocks 

 only differ from the permanent base of an undershi'ub 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- 

 grovmd, and produces one or more buds. Tliis branch, or a portion of it, 

 alone survives the winter. In the foUowdng year its buds produce the new 

 stem and roots, whilst the rest of the plant has died away. These annual 

 stocks, called sometimes hybcrnaada^ offsets, or stoics, 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 tnber 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 bud at the top. A potato 

 is an annual tuberous rootstock with several buds. 



20. A bulk 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 bulblets or offsets in the axils of its scales. 



21. Bulbs are, 



scahj, 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 fi-uit. 



24. Stems are, 



e7'ect, 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 groimd ; 

 creeping, when they emit roots at their joints. This tenn is also 



applied to rhizomes or roots, when they spread horizontally. 

 tufted {ccds2ntose)y 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 tivine when they support themselves by 

 winding spirally roimd 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. Sarmentosc stems or branches are woody, 

 long, and weak. 



b 2 



