OF ROOTS.
In defining the parts of vegetables, it is found most commodious to begin from the bottom, proceeding upwards. Hence the root, which is the first part pro duced by a germinating embryo, comes first under consideration. Its presence seems necessary to plants, as it serves to fix and hold them in the earth, from which they imbibe nourishment through their elementary tubes. Sea-weeds, how ever, afford an exception to this, for they are nourished by their surface, the root serving only to fix them to a convenient spot.
A root is either annual, biennial, or pe rennial. The first kind live but one sea son, as barley ; the second survive one winter, and perish at the end of the fol lowing 'summer, after perfecting their seed, like wheat ; if, however, any cir cumstances should prevent their flower ing, they may live several years till that event takes place. Perennial roots are such as remain and produce blossoms for an indefinite term of years, like those of trees and shrubs in general, and of many herbaceous plants whose stems are an nual.
The body of the root is denominatee caudex ;- the fibrous, which is the only essential part, radicula. This latter i; ' strictly annual in all cases, and is what serves for absorbing the nutritious fluid; of the soil. It is necessary for the bota fist, as well as the farmer and gardener , to be well acquainted with the severs kinds of roots, which diflPr • their nature and functions. Those o a fleshy nature most powerfully resist drought, and are, as Dr. Smith has sug gested, reservoirs of the vital energy of the vegetable. We have, with the per mission of this gentleman, adopted in the following pages those leading ideas upon the subject before us, which are detailed and exemplified more at length in his Introduction to Physiological and Sys tematical Botany," to which work we must refer those of our readers, who wish for more deep information titan our limits will allow.
Roots are distinguished as follows : 1st. A fibrous root, radix Prow, con sists entirely of fibres, as in many grasses, and a number of annual herbaceous plants. These can but ill bear a continu ed deprivation of moisture or nourish ment. The fibres carry what they absorb
directly to the base of the stem. Botany, Plate 1. fig. 1.
2nd. A creeping root, repens, is a sort of subterraneous stem, spreading hori zontally in the ground, throwing out abundance of fibres, as in mint and couch grass. Weeds furnished with such a root are amongst the most pernicious, being so difficult to eradicate. Nature, however, having furnished them with so powerful a niode of increase, is very sparing in the production of their seeds. Fig. 2.
3rd. A spindle-shaped root, fusiformis, is common in biennial plants, though not confined to them. The radish and carrot have spindle-shaped roots, producing nu merous fibres for the absorption of nutri ment. Such roots may be transplanted with great safety in the torpid season of the year. Fig. 3.
4th. An abrupt or stumped root, pre. morsa, like that of the primrose, is as it were bitten off; hence many plants fur nished with it have obtained the whimsi cal name of devil's-bit. Fig. 4.
5th. A tuberous or knobbed root, tube rosa, a very important sort, appears under a great diversity of forms. In the potatoe it consists of fleshy knobs connected by. common stalks or fibres ; these knobs are biennial, formed in the course of one sea son, and destined to produce fresh plants the following year. This is the case with the oval or hand-shaped roots of the orchis tribe. Some herbs, indeed, have perennial knobs to their roots. Fig. 5.
6th. A bulbous root, basso, consists of a kind of subterraneous bud, being either solid, as in the crocus ; tunicate, as in the onion ; or scaly, like that of the lily. Fig. 6. These roots, like the knobs abuse mentioned, are reservoirs of nou rishment, or rather of the vital powers, during the winter. After flowering and leafing their herbage and fibres decay, and the roots may then be removed or kept out of the ground for a time without any hazard. When fresh fibres are formed it is fatal to disturb them.
7th • A granulated root,granulata, agrees in physiology with the last, being a clus ter of little bulbs or scales connected by a common fibre, as in the white saxifrage and wood sorrel. Fig. 7.