A practical acquaintance with the roots of different trees and shrubs will soon teach the gardener how to discriminate their distinctive characteristics of growth and smell, so as readily to distinguish the roots of the ubiquitous Birch, the Portugal Laurel, Laburnum, Quince, Scotch Fir, etc, or the Vine, or the beautiful roots of the seedling Asparagus, or the roots of the Tussilago Farfara (Coltsfoot), or the Couch-grass, or the Bell Bine, or the root of the Raspberry. Some plants, such as Dracaenas and tuberous-rooted Geraniums, can be readily propagated by cuttings made of the roots.

Some plants, such as Ivy, are furnished with what are called adventitious roots, but as they are on the stem they are not true roots; nevertheless such roots after they enter the soil perform the functions of true roots.

Some plant-growths are often called roots which are not so: they are prostrate or underground stems, such as the root of the Iris, which is supplied on its under surface with rootlets, on its upper surface with leaves, and is properly called a rhizome. The root of the Potato is an axillary bud on an underground stem. The corm of the Cyclamen, as it is sometimes called, is in reality an abrupt rhizome or root-stock, analogous to that of the Primulaceae, to which family it belongs.

Bulbs are regarded as undeveloped stems or underground leaf-buds, from which true roots will grow, but never a tap-root. They are formed from seed, or from the axillary buds on the stem of the bulb, and when perfected are of annual duration only: the same Tulip does not blossom the second time. There are tunicated bulbs, as Hyacinthus orientalis; scaly bulbs, as Lilium candidum; and these scales, on removal from the bulb, may be propagated, and will form bulbs. Some plants of the Araceae family will produce tuber-buds above ground; other tuberous-rooted plants, such as Gesneraceae, will produce, from the leaf, roots which soon develop tubers like the parent plant, if scientifically treated for that purpose, of which more •will be written hereafter.

Pseudo bulbs, or pseudo tubers, of Orchids, are of green colour above ground, thickening at the base of the stem. In the Dendrobium they assume the form of an ascending stem, and bear on it the beautiful flowers. The function is that of a reservoir to supply to the next pseudo bulb and flower nourishment. The pseudo (stemlike) bulb of Dendrobium possesses the faculty, on division into cuttings, of throwing out aerial roots and forming a new plant: possibly the joints in the stem are allied to nodes, if not identical.

The organisation of the roots of the plant is so beautifully adapted to the functions they have to perform, that they go, as it were, in search of and to select their food, often long distances, penetrating through crevices in the soil. The root-cells are considered to be the immediate absorbers, and are easily and often replaced; but there is no sufficient reason for considering that in dicotyledonous plants they are formed annually, as has been sometimes stated. Water in some form, either as vapour or as liquid containing in solution carbon dioxide (carbonic acid), ammonia, and saline elements, is the medium by which plants absorb their food.

So great is the attractive force of the liquid in a plant set in motion by the action of these root-cells, and of a certain amount of heat which is necessary, and of the cell-walls of the root, stem, and leaves, that the absorbed liquid passes from cell to cell, filling them up, passing into the stem, distending the cell-walls, and enlarging the same, and thence to the leaves, where it is elaborated, and the liquid is called sap. This process of the strange phenomenon of liquids attracting each other through a vegetable tissue, as the cell-wall or membrane of cellulose, is known by the name of osmose (osmosis, or impulse): the outward flow is called exosmosis, the inward flow is called endosmosis. Its power varies: some organic substances have little or no osmose, others produce it to a great extent, and others have a negative osmose. This osmotic action has been called hydrostatic pressure, and in grape-sugar it is very great, as may be readily seen in the warmth of spring, when Vines bleed, as it is called, if cut before the leaf-growth has commenced to utilise the sap.

Schleiden says that endosmosis is assisted by absorption of cell contents, caused by evaporation of the watery fluid through the leaves: in other words, as all the cells are filled with fluid, evaporation empties them, and therefore the greatest flow of sap is where, and when, the plant has most evaporating organs.

A good example of the power of endosmotic force may be seen sometimes in a vinery, when a young rod is carried up from an old Vine: the force is so much stronger in the young than in the older rods, that they will be prejudicially affected by their younger relative, until the equilibrium is restored by the flow of sap equally, in the old and new wood, which will probably not be the case during the first year of its growth. The flow of liquid induced by exhalation or evaporation is not necessarily a process of growth, although, like it, it is towards the youngest portions of the plant; it may go on after the growth of foliage on a tree is completed.

Each plant has a stem, either above or below the ground (the plumule of the seed elongated), for supporting leaves, buds, or flowers, and through it the liquid-sap absorbed by the roots and the gases absorbed from the atmosphere and decomposed in the leaves circulate through the plant structure. The stem is either simple or branched; it may be more or less destitute of leaves, as in different species of Cactus, Euphorbia, and Stapelia, where the epidermis acts the part of a leaf. The stem is terminated by a bud (called punctum vegetationis) at every point, consisting of embryo leaves packed closely together, and at intervals on the stem or branch are nodes or joints, from which buds and leaves grow (in Pinks, Carnations, and Grasses the nodes are very much swollen); and the spaces between these nodes are called internodes.

The stem may be erect (erectas), or procumbent (procumbens), or creeping (repens), or reclining (reclinatus), or arcuate (curved), so as to form part of a circle, as the Bramble; or clinging to any object for support by fibres, as the Ivy (radicans); or climbing by means of tendrils, as the Vine (scandens); twining spirally round other plants, as Honeysuckle (volutilis); or supple, pliant, whiplike, as Jasmine (flagelliformis); or trailing, as a runner of the Strawberry (sarmentosus); straight, as in Lily (rectus); two-ranked when branches spread in two horizontal directions (distichus); branched, as in the Apple (ramosus); proliferous (prolifer), bearing branches on the summit of the others, as in Scotch Fir; articulate-jointed, as in the Indian Fig family (Opuntia), etc.

The shape of the stem may be either round, terete (teres) or two-edged, ancipital (anceps) or three-edged or triangular (triquetrous), or square (quadrangularis), or five-sided (quinquangularis), etc.

The surface (epidermis) of the stem may be either smooth (glaber), viscid (viscidus), warty (verrucosus), papillose (papillosus), rough (scaber), downy (tomentosus), shaggy (villosus), glaucous (glaucus), striated (striatus), furrowed (sulcatus), spotted (macidatus); sometimes there are states of the epidermis, or attachments to it, producing hairs, glandular hairs, prickles, etc, but thorns are attached to the wood.

In its earliest stage the stem consists of cells closely packed together, which, from their crowded state and consequent pressure during growth, assume various shapes called cellular tissue; and if the texture of it is hexagonal, it is called parenchyma (from its supposed likeness to liver or lungs). There are other forms of cellular tissue in it, as vascular tissue, which includes woody tissue and fibro-cellular tissue (cell with a spiral coiled up in it), but one and all these forms are only modifications of cellular tissue.

Labore Vinces.