branches, the quality of whose fruit is of very unusual excellence. These facts seem capable of being applied to many important improvements in fruit management.

The foregoing are the principal advantages which arise from training plants; let us next consider what disadvantages there may be. The only trees which at all approach in nature the state of trained plants are climbers and creepers, whose stems, unable to support themselves, cling for a prop upon whatever they are near; some of them enclose the stem of another plant in their convolutions; others simply attach themselves by means of tendrils as the Vine, by hooks as the Combretum, or by other contrivances; and some, like the Ivy, lay hold of walls, rocks, or the trunks of trees, by their minute roots. To none of these can that motion be necessary to which plants are naturally exposed, and which, as has been already seen (p. 161.), is of so much importance to the healthy maintenance of their functions. Hence it is, that among fruit trees the Vine never suffers from being trained: indeed its anatomical structure is specially suited to such a mode of existence; while all erect trees, of whatever kind, whose branches nature intended to be rocked by the storm, and perpetually waved by the currents of air to which they are exposed, in all cases suffer niore or less.

One of the commonest and worst diseases in

duced by training is a gradual impermeability of tissue to the free passage of sap, which appears to stagnate, so that in time the branches become debilitated and juiceless: the obstruction to the flow of the sap tends to produce coarse shoots from various parts of the branches, and especially from the roots. The cause of this seems to be the too rapid deposit of the sedimentary matter of lignification*, and to be induced by want of motion and excessive exposure of the leaves and branches to the sun. The effect of the latter is to inspissate all the juices, and to promote their formation ; while the former increases the evil by not keeping the fluids in rapid circulation: just as we know that a slow stream, from a muddy source, deposits its impurities much more copiously than a rapid stream. As this evil arises out of the operation of training, and seems to be inseparable from it, there will bę no expectation of a remedy being discovered.

The increase of the saccharine quality of fruit is by no means an advantage in all cases; it improves the peach, the nectarine, the pear, and the plum, in which sweetness is the great object: but it deteriorates the apple and the apricot, which are chiefly valued for their peculiar mixture of acidity and sweetness.

The protection received in the spring by trees trained upon walls exposed to the sun, while it * See Introduction to Botany, ed. 3. p. 3.

advances the period of flowering, at the same time causes it to take place at a season when they are not sufficiently secure from spring frosts; and hence the necessity of protecting such plants artificially by coping, screens, bushes, curtains, and other contrivances. It is on this account that the

utility of flued walls is so much diminished, and that they are found, in practice, more valuable for ripening wood in autumn, than for guarding blossoms in the spring.

CHAP. XV.

OF POTTING.

WHEN a plant is placed to grow in a small earthen vessel like a garden pot, its condition is exceedingly different from that to which it would be naturally exposed. The roots, instead of having the power of spreading constantly outwards, and away from their original starting point, are constrained to grow back upon themselves; the supply of food is comparatively uncertain; and they are usually exposed to fluctuations of temperature and moisture unknown in a natural condition. For these reasons, potted plants are seldom in such health as those growing freely in the ground; but,

as the operation of potting is one of indispensable necessity, it is for the scientific gardener, firstly, to guard against the injuries sustainable by plants to which the operation must be applied; and, secondly, to avoid, as far as may be possible, exposing them to such an artificial state of existence. That the latter may be done more frequently than is supposed will be sufficiently obvious, when we have considered what the purposes really are that the gardener needs to gain by potting.

The first and greatest end attained by potting is, the power of moving plants about from place to place without injury; greenhouse plants from the open air to the house, and vice versâ; hardy species, difficult to transplant, to their final stations in the open ground without disturbing their roots; annuals raised in heat to the open borders; and so on and, when this power of moving plants is wanted, pots afford the only means of doing so. It also cramps the roots, diminishes the tendency to form leaves, and increases the disposition to flower. Another object is, to effect a secure and constant drainage from roots of water; a third is, to expose the roots to the most favourable amount of bottom heat, which cannot be readily accomplished when plants of large size are made to grow in the ground even of a hothouse; and, finally, it is a convenient process for the nourishment of delicate seedlings. Unless some one of these ends is to be

answered, and cannot be effected in a more natural manner, potting is better dispensed with.

That it may be advantageously dispensed with, in many cases, is evident from several facts more or less well known. The nurserymen prefer pricking out" their delicate seedlings into pans, or movable borders, instead of pots; and they always thrive the better. In conservatories, the necessity of shifting plants from place to place may be often avoided; while, under judicious management, those which are planted in the open soil have greatly the advantage of others, both in healthiness and easiness of management; and there is no doubt that Pine-apples will succeed better unpotted, if planted freely in soil exposed to a proper amount of bottom heat. This was first asserted by Mr. Martin Call, one of the Emperor's gardeners at St. Petersburg (Hort. Trans., iv. 471.), and has been since practised very successfully by others. In the year 1830, a pineapple, obtained by this treatment, weighing 9lb. 4oz., was sent to the King of England by Mr. Edwards, of Rheola; and the success of other growers, in the same manner, has been remarkable. (See Hort. Trans., n.s., i. 388.)

The exhaustion of soil by a plant is one of the most obvious inconveniences of potting. The organisable matter in a soluble state, contained in a garden pot, must necessarily be soon consumed