Fig. 71.—Budding or cushion grafting. and fruit for which the parent may have been celebrated. We need not enlarge here on tie’importance of this principle; it is applied most successfully in horticulture, where some delicate species of fruit or flowers is produced on a stem destitute of the vigour necessary to nourish and bring it to maturity The leaf-bud is thus a coneform organ placed on the axis of a leaf, in short, a rudimentary leaf or branch formed as the growing season 18 closing, and is the nidus in which the leaf will be formed in the coming spring, rather than parts of a leaf in a rudimentary condition. The central growing point (Fig. 60) is composed of cellular tissue possessing special powers of vitality and growth, and closely connected with the pith of the stem. From this point

ea58 THE VEGETABLE WORLD.

all the future leaves have their development, and it is, in all probability, the organ whereby the circulation of the sap is effected after the winter’s repose. This growing point has a certain analogy with the embryo in the seed, inasmuch as both tend to growth and reproduction; but they differ in this, that the leaf-bud needs no fertilisation for its development, and propagates the individual as well as the species, while the embryo imperatively * needs fertilisation, and continues the species only.

Fig. 72.—Dockweed.

Fig. 73 —Italian or Stone Pine.

Bovucus anp BrRANcHEs.

The branch is formed by the development of the bud, and this bud, as we have said, is the axil of the leaf. The branch being only a secondary stem emanating from the

principal trunk, necessarily presents the same modifications of orm, of structure, and of disposition of the leaf, which we observe in the trunk, properly so called; but the resemblance between the stem and its branches is not always complete; thus

Fig. 74 —Branch of Butcher’s Broom (Ruscus aculeatus). in the Butcher ’s Broom (Ruscus aculeatus), Fig. 74, the branches are short, and at their enlargement take so immediately: the form of leaves, that the’ early botanists considered them to be such. But an attentive observer will not be deceived if he considers that these flattened organs with their foliaceous appearances bear at

their axils scales which are the true leaves, and carry flowers which are the exclusive characteristics of branches.

In some plants the branches expand considerably, but in most others they remain slender; their terminal bud abortive, they become pointed and hardened at the extremities; in short, they are changed into spines as in the Hawthorn (Crategas oxycantha).

A modification extremely curious and interesting in the form

Fig. 75.—Subt i f Poiato,

and consistence of branches occurs in the Potato (Solanum tuberosum),

Fig. 75, which is developed under ground. The subterranean part of the stem is not green, and the leaves, if we can call them 80,

are only small rudimentary scales, at whose axils the branches, which extend themselves more or less horizontally, develop themselves, and are charged with abortive leaves. These branches, which are thin and slender at their origin, swell at their extremities, are filled with a green pulverulent matter, and finally become the tuber, which we recognise as the potato. In short, if we examine a potato, we see that it is covered at intervals with eyes, or scales. At the axils of these scales a bud is found; every one knows that these buds, when the potato is stored in dark cellars, push out long slender shoots at the return of spring. These are their true branches or stems. The fact that the parts here described are — really portions of the stem, is curiously proved by the following instance recorded in the Gardener’s Chronicle, vol. ii. p. 89 A potato plant had grown underneath an inverted flower-pot in a dark cellar, where it had formed itself into a perfect miniature potato _ plant. Being only surrounded by air, it had thrown out its with the ‘ grown it had resistance, with no and meetingbranches, above — done have would plant ordinary as an regularity same ground. The set, or old tuber, was shrivelled up, and formed a wrinkled knob, out of which grew many branches and branchlets. 4 Of the latter, some had become thickened at the point, resembling young potatoes; others, having no power of extending themselves, q had swelled close to the parent tuber. All wore covered scales, —

’ the rudiments of leaves. At first sight the plant appeared as if 4 it had been unable to form roots, but a more minute inspection:: showed that they were really beginning to form here and there 10 q many places upon the surface of the branches.

There is a great difference between tubers—between the Potato and the Dahlia, for instance. The tubercule of the Dahlia may be called a true root; it has no vital node, or joint. On the other — hand, the stem of the potato bears many of these vital knots.

The length and direction of the branches, as compared with the parent stem, are extremely varied, and this variety tends to give to each plant its special appearance, its peculiar physiognomy. If the lower, and consequently first formed branches, continue 0 extend themselves in the same proportion, and the upper ones are shorter as they approach the summit, the form of the tree i8 ‘conicalor pyramidal, as in the Firs (Fig.76). If the central branches

extend beyond the lower ones, the form is round or oval, as is the

Fig. 76.—Spruce Fir (Abies),

case with the Horse Chestnut (sculus Hypocastanum), Fig. 77.

If the upper branches take a fuller development, as in the Italian Pine, Fig. 73, the summit of the tree expands in an umbrella form, and has been aptly compared to the spreading of volcanic

scoria, expanding over the mouth of 2 crater, before it descends again

FAGUET. DEL.

to the earth. In all these instances the direction of the branch 1s decided by the manner in which the bud is inserted in the stem,

and the direction and growth of the branch give its particular

a appearance to the tree. Branches issue from the stem at all

imaginable angles, sometimes at right angles, sometimes at angles

Fig. 78.—The Cypress. so acute as to seem at a little distance to rise with the bole of the F

tree. The tapering branches of the funereal Cypress (Cupressus), as compared with a kind of dome formed by the branches of the Oak (Quercus), or the Cedar, give us some idea of the contrast which the two kinds of ramifications present. The Lombardy Poplar (Populus fastignatus) carries the contrast still further.

Fig. 79.—Weeping Willow.

The aspect of each of these trees places in bold relief the influence which the different modes in which the bud is inserted exercis? upon the ramifications of the branches and the form of the tree-

In some trees the branches take a direction which seems invers€ to the usual habit of trees. In place of rising towards the skies,

the branches appear to incline towards the earth with a drooping aspect. The Weeping Willow, represented in Fig. 79, presents © a striking and well-known example of this habit of growth. The F ) aod

long slender branches of this elegant tree fall by their own weight. But the habit is not confined to this tree. The ash and other trees are capable of being trained to it, and gardeners avail themselves largely of the habit, planting the banks of water basins, ponds, and brooks with the one, and forming shady places on lawns by means of the others. The Willow is at once elegant and sad in its aspect. The branches of the Sophora of Japan (Sophora Japonica), or the Weeping Sophora, resemble the Weeping Willow in many respects, but they possess a certain rigidity at their extremities, which gives a tendency to resume the upward direction, Fig. 80.

We have said that a branch may be considered as a secondary stem, emanating from the principal one, from which it draws its

Fig. 81.—Propagation of layers.

nourishment. But if we give this secondary stem or branch another source of nourishment, it may be separated from the rincipal axis which carries it, and become a free and distinct individual of the same species. Upon this natural fact has been root-grafting, well known ™ founded the process of layering, or horticulture; bending a flexible branch towards the humid soil prepared for the purpose, the gardener maintains it in its position by

pegging down, as represented in Fig. 81, until it has thrown out roots. These roots being developed, it contains within itself all the elements of life. The branch may be separated from the stem, from which it no longer requires support. This process is known

as grafting by inclination. But every branch which it is desired to layer may neither be within reach of the soil nor sufficiently flexible to bend to the extent requisite. In such cases the soil must be'raised to the branch. To effect this, vases or flower-pots

_ of various forms are employed, which are filled with earth, and maintained at the necessary height, the branch being placed in it traversing the vase in contact with the soil, as in Fig. 82. The soil being maintained in a humid state, the portion of the branch in contact with it is not slow to push forth its adventitious roots, which are soon present in sufficient numbers. In due time the branches may be separated from the parent stem, and transplanted elsewhere. This is called layering by approach. Propagating by slips or cuttings differs from layering only in this, that the part of the plant employed in the process of multiplication is detached at once from the parent plant, and completely abandoned to the powers of nature. Cut a branch even of considerable size from a willow or poplar; give it a clean sloping cut across a joint or node, and bury it in humid soil, it will immediately push out adventitious roots, and soon begin to grow a new and independent willow or poplar. But all plants will not so readily accommodate themselves to this easy mode of multiplication. There are some plants which will not take, to use the consecrated term, without the aid of many complicated. artifices; there are even some which resist all means known of propagation by slips; in short, the slip often finds itself subject to these alternatives—to die of inanition, for want of sufficient moisture, or to rot from overmuch liquid. The problem for the operator to solve, in order to favour the production of roots, is to establish a proper equilibrium between the aqueous losses to which the slip will submit, and the quantity of water which it absorbs; and to do so is not without its difficulties. But this is not the place to explain the processes by which these operations are successfully performed. We must content ourselves with remarking that the process is not confined to slips or cuttings of branches, as cited above. Cuttings may be made from rhizomes, from leaves, and even from parts of a leaf. But this last process is only employed for certain exotic plants; the inhabitants of our hot-houses which never bear fruit, and scarcely throw out branches.

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