afford a longer succession of produce, owing to the succession of young shoots which are caused to spring from its larger branches and stems; and, in all cases when trees can be made to retain their health in exposed pots, the

Fig. XCIV.

period of the maturity of their fruit is very considerably accelerated." (Hort. Trans., vii. 258.) This seems to have led Mr. Rivers to his happy idea of orchard-houses and miniature fruit-gardens, now so much in request.

The best method of counteracting the injurious effects of exposure to the air is by employing double pots (Fig. XCIV.), as recommended in the Gardeners' Magazine, ix. 576, and by Captain Mangles in his Floral Calendar, p. 44; the space (b) between the two pots being filled up with moss or any other substance retentive of moisture.

There are two ingenious contrivances of this nature: one by Mr. Robert Brown, potter, at Ewell, and the other by Mr. William Rendle, the nurseryman at Plymouth. In both cases the object is the same, namely, to have a double-sided pot in one piece. It is obvious that by such contrivances, if the sides of a pot are left empty, the stratum of air contained between them will prevent the earth from becoming heated; and if they are filled with water, the inconvenience of over-watering, on the one hand, or over-drying, on the other, will be prevented in summer, because water will be continually filtering slowly through the inside lining as the roots require it. The latter reason renders them valuable for striking cuttings, and for window gardens, where it is almost impossible to keep plants duly supplied with moisture. Doubtless, in winter, if water be introduced between the sides of this kind of pot, its inner surface will be always wet; the young roots will receive too much fluid, and the plant will die: but if the empty space be permitted to remain empty, the inner portion of the pot receiving moisture only from the watering required for the well-being of the plant, the outer side having water occasionally poured on it, or the pot being immersed for a few minutes in it, the sides of the pot will be kept so fully saturated, that they will be constantly giving out into the empty space a vapour, by which the inner portion of the innermost pot (towards which the young roots always incline, and with which they are in contact) will be kept sufficiently cool and moist, and the roots will be preserved from injury."

a

Of Rendle's pots (Fig. XCV., a and b), a differs in no material degree from Brown's, except that its lower angles are made stronger, and it is better contrived for drainage; the other (b, which was proposed for striking cuttings) has a central hollow space which enables

Fig. XCV.

the bottom-heat to be better maintained. Neither of the plans seem, however, to have found favour among gardeners, probably on account of the expense; indeed, it is manifest that three common pots of unequal size can be readily so arranged as to produce all the effect of even Rendle's second sort.

Of course the inconveniences thus described are principally sustained by plants in small pots. When the quantity of earth is considerable, as in tubs or the largest kind of pots, the loss of water through the sides is of little moment, and the variation of temperature is more than counteracted by the large surface exposed to the direct influence of the solar rays. In these, as in all other cases, perfect drainage is of the greatest service, and should be carefully secured by placing an abundance of broken tiles, potsherds, &c., in the bottom of a pot, so as to prevent the stagnation of water about the roots.

Mr. Macnab, in his excellent practical treatise upon the cultivation of Cape Heaths, points out very forcibly the value of good draining to that class of plants. There is scarcely any danger, he says, of giving too much draining; and, in order to effect this essential object still more perfectly, he, in shifting his Heaths, constantly keeps the centre elevated above the general level of the earth in the pot or tub, so that at last each plant stands on the summit of a small hillock.

In order to counteract the risk of excessive drainage, without in reality diminishing it, great advantage is derived from the introduction into the earth of fragments of some absorbent stone. Mr. Macnab uses 66 coarse soft free-stone broken into pieces from one inch to four or five inches in diameter;" because in summer these stones retain moisture longer than the earth, and in winter allow a free circulation of any superabundant moisture.

The mode of effecting drainage practically is thus described by Mr. W. Moody, an experienced correspondent of the Gardeners' Chronicle:"The materials for this purpose should be perfectly dry and free from dust, whether they be crocks, charcoal, or sandstone; they should be broken into different sizes, each size being placed separately; thus, if I were using 3-inch pots, I first clean the pot well inside if required, then place a piece of crock at the bottom, nearly as large as will cover it, but convex, so as to allow the water free egress; on this I place a layer of broken crocks, or other material, about the size of Beans, and on this again a slight layer about the size of Peas. When I use pots of a larger size, I use larger pieces, always keeping the coarsest at the bottom and the smallest at the top. With very few exceptions, the plants will be benefited by placing a thin layer of turfy loam or peat over the drainage, as this keeps the smaller particles of earth from being carried downwards. Although there is no fear of drainage being impaired, if properly constructed, yet, to make doubly sure, let each pot be crocked as regularly as possible, one having no more drainage than another, so that in the next shift each may get the same proportion of soil as well as drainage. Pieces of sandstone mixed with the soil are very useful in drainage for hard-wooded plants, as are also pieces of charcoal and bone-dust for soft-wooded ones; in either case the roots will be found closely adhering to these lumps. There are many gardeners who say, 'I have no time to attend to such a routine of breaking and layering;' but crocks do not spoil by being broken and sorted in the coldest day in winter, nor yet if done in wet weather, when nothing can be done out of doors. The different sizes may be placed in large pots, and put somewhere out of the way, where they will be dry until the crocks are wanted for use, which is generally in spring and summer seasons, when work is pressing; thus time is saved by having crocks previously prepared, and plants are benefited by judiciously arranged drainage, which is sure to be effectual." This advice is selected from among many others, because it seems to describe the best kind of practice in the fewest words. Another, and very good method, is the following:

"The ordinary way of putting at the bottom of the pot a large

quantity of crocks is but a clumsy proceeding, and one which, if it affords an opportunity for roots to spread themselves freely, affords also a harbour for worms, slugs, woodlice, and other vermin. To remedy this, I put at the bottom a piece of perforated zinc, an inch and a quarter, or more, square, according to the size of the pot, so as completely to cover the hole; this perforated zinc may be had for a trifle of any brazier or tin-plate worker, and may, by the help of a strong pair of scissors or small shears, be readily cut to the requisite size; upon this I place a small potsherd, with its convex side upwards, taking care that by resting partly upon the zinc it renders it immovable. I then put in a quantity of good moss so as to form a layer of a third of an inch, or more, thick, when pressed together by the mould, and proceed to finish as usual the operation of potting the plant. I have found this method to succeed perfectly: constant drainage is effected; the moss, particularly with the addition of the potsherd, prevents the earth from choking the holes of the zinc, and by partial decomposition, where it is in contact with the soil, affords an agreeable receptacle for the roots of the plant, in which they appear to delight. All sorts of vermin are excluded; the operation of shifting is facilitated, as the earth comes out of the pot unbroken; and it is, moreover, a much more cleanly process than the one commonly used. I must, however, add, that if the pots thus treated are placed out of doors, it will still be desirable that they should be put upon tiles or slates, or something of the sort; because, as the compost is generally rich, the worms will be attracted by the water which drains from it, and although they cannot get into the pot, if the bottom, inside, be level so as to keep the zinc close all round, they will fill the hole below it with their casts, and thus impede the drainage."

Materials for drainage abound among the refuse of all gardens. Broken pots, called crocks, are usually employed, and, if not burnt too hard, are amongst the more useful. It is, however, of considerable importance that the material, be it what it may, should be soft and porous. Burnt clay, pounded bricks, fragments of charcoal, all which, by virtue of their porosity, retain gaseous matters, are among the best, inasmuch as they not only drain soil, but feed plants. For the same reason bones, crushed with a hammer into pieces varying in size from that of a hazel nut to a walnut, may perhaps be regarded as the best of all.

If woody plants are allowed to remain growing in the same. pot for many years, as is sometimes the case, one of two things must happen: either the roots, matted into a hard ball, become so tortuous and hard as to be unfit for the free passage of sap through them; or they acquire a spiral direction. In

440

CORK-SCREWED ROOTS.

either case, if such plants are turned out of their pots in a conservatory, or in the open ground, with a view to their future growth in a state of liberty, new roots will be made with difficulty, and it will be a long time before the effects of growth in the free soil will be apparent. Where the spiral or corkscrew direction has been once taken by the roots, they are very apt to retain it during the remainder of their lives; and if, when they have become large trees, they are exposed to a gale of wind, they readily blow out of the ground, as was continually happening with the Pinasters some years ago, when the nurserymen kept that kind of Fir for sale in pots. In all such cases as these, the roots should be carefully disentangled and straightened at the time when transplantation takes place. To prevent the possibility of this occurrence it is not unusual to

Fig. XCVI.-Root of Pinus Laricio.

place trees intended for transplantation in old baskets. Through their wicker sides the roots readily penetrate, and when this has happened, the half decayed baskets are lifted and "potted" in other baskets of a larger size.

The annexed sketch of the root of a Laricio, taken up at Hatfield, by Mr. William Ingram, the gardener there, after having been planted ten years, illustrates the effects of corkscrewing better than any description.

Under ordinary cir cumstances a potted plant when young, is placed in

as small a pot as it will grow in, and is transferred from time to time to larger pots as it advances in size. If this is done,