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PRUNE ROOTS BEFORE PLANTING.

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this fluid, and often becomes the seat of disease which spreads to parts that would otherwise be healthy. To this it may be added that decaying roots become the seat of dry-rot fungi, which, once established, rapidly introduce their spawn among the living tissues, and produce diseases which only end in death.

When, however, the wound is made clean by a skilful pruner the vessels contract, and prevent the introduction of an excess of water into the interior; the wound heals by granulations formed by the living tissue, and the readiness with which this takes place is in proportion to the smallness of the wound. It may be sometimes advantageous to remove large parts of the coarser roots of a tree, even if they are not accidentally wounded when taken up, the object being to compel the plant to throw out, in room of those comparatively inactive subterranean limbs, a supply of young active fibres. This is a common practice in the nurseries when transplanting young Oaks and other tap-rooted trees, and is one of the means employed by the Lancashire growers of Gooseberries, in order to increase the vigour of their bushes; in the last case, however, the operation is not confined to the time when transplantation takes place, but is practised annually upon digging the Gooseberry borders. The reason why cutting off portions of the principal roots causes a production of fibres appears to be this: the roots are produced by organizable matter sent downwards from the stem; that matter, if uninterrupted, will flow along the main branches of the root, until it reaches the extremities, adding largely to the wood and horizontal growth of the root, but increasing, in a very slight degree, the absorbent powers; but if a large limb of the roots is amputated, the powers of the stem remaining the same, all that descending organizable matter which would have been expended in adding to the thickness of the amputated part is arrested at the line of amputation; and, unable to pass further on, rapidly produces granulations to heal the wound, immediately after which young spongioles appear, soon establish themselves in the surrounding soil, and become the -points of new and active fibres.

By many excellent planters, the advantage of deluging the

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SUBSTITUTE FOR ROOT-WATERING.

roots with water, when newly planted, is much insisted on; and in the case of large plants, particularly evergreens, it is, undoubtedly, an essential process, partly because it causes the flagging and injured roots to be immediately surrounded by an abundant supply of liquid food, which, if the operation be skilfully performed (see Macnab's Treatise, pp. 24 and 25), will not subsequently fail them; and partly because it is the only means we possess of embedding with certainty all the fibres in soil. When the earth is reduced to the state of puddle, it will settle round the finest roots, and place them as nearly as possible in the same condition, with regard to the soil, that they were in before the plants were removed. But the operation of puddling is unnecessary to small plants, if removed at a proper season of the year, especially to deciduous trees of all kinds; and it may be injurious. This was long ago stated by Mr. Knight (Hort. Trans. iii. 159), who found by experience that when trees are very much out of health, in consequence of having become dry, excess of moisture to the roots is often fatal. This appears to arise from the languid powers of the plant being insufficient to enable it to decompose and assimilate the water rapidly introduced into its system through wounds in its root, or by the hygrometrical force of that part; under such circumstances, water will dissolve the mucilaginous and other matters intended for the support of the nascent buds, which matters then putrefy, lose their nutritive quality, and destroy the tissue. The substitute for root-watering contrived by Mr. Knight in such cases was, to keep the plants in a situation shaded from the morning sun, and to moisten their bark frequently; by these means water is presented to them slowly through the young cortical integument, which, partaking of the nature of a leaf, slowly absorbs it, probably decomposes it, and transmits it laterally through the liber into the alburnum, where it finds itself in the ordinary channel of the ascending sap, and thus enters the system of circulation. In this way Mr. Knight succeeded in preserving American Apple-trees, which reached him in the middle of April, in so bad a state that they seemed "perfectly lifeless and dry," and "much better. fitted for fire-wood than for planting."

CHAPTER XVII.

OF THE PRESERVATION OF RACES BY SEED.

THE manner of preserving the domesticated races of plants by the ordinary means of propagation, such as cuttings, layers, grafts, and so on, has already been explained; there are, however, other topics connected with this important subject which require to be touched upon.

Propagation by division is inapplicable to annuals or biennials, or at least can be practised upon only a very limited scale, and for such plants the gardener has to trust to seeds alone. But it is an axiom in vegetable physiology that seeds reproduce the species only, while buds (that is, propagation by division) will multiply the variety; and this is undoubtedly true as a general rule. But the skill and care of the gardener often enable him to perpetuate by seed the many races of cultivated annuals, varieties of the same species, improved and altered by centuries of domestication, with as much certainty as if he were operating with cuttings. In a well managed farm we see the various breeds of Turnips and Corn preserving each its own peculiar character unchanged year after year, and yet they must all be propagated by seed alone; and in gardens the varieties are innumerable of Peas, Lettuces, Cabbages, Radishes, &c., whose purity is maintained by the same means. The manner in which this is effected is of the first importance to be understood.

Although it is the general nature of a seed to perpetuate the species only to which it belongs, and it cannot therefore be relied upon, in ordinary cases, to renew a particular variety of

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SIMILITUDE RETAINED BY SEEDLINGS.

the species, yet there is always a visible tendency in it to produce a seedling more like its parent than any other form of the species. Suppose, for example, the seed of a Ribston Pippin Apple were sown; if untainted by intermixture with other varieties, it would produce an Apple-tree whose fruit would be large, sweet, and agreeable to eat, and not small, sour, and uneatable like the Wilding Apple or Crab. The object of the gardener is to fix this tendency, and he does it by means not unlike those employed in the preservation of the races of domesticated animals, namely, by "breeding in and in," as the phrase is. An example of this will be more instructive than a dissertation. The Radish has, when wild, a long pallid root; among many seedlings one was remarked with roots shorter and rounder, and more succulent than the remainder; this was a "sport," to which all plants are subject. Had that Radish been left among its companions, and the seed saved from them all indifferently, the tendency would have disappeared for that time; but its companions were all eradicated, and the better one produced its seed in solitude. The crop of young plants obtained from this Radish was, for the most part, composed of individuals of the wild form, but several preserved the same qualities as the parent, and some, perhaps one only, in a higher degree: in this one, then, the tendency was beginning to fix. Again were all eradicated, except the last-mentioned individual, whose seeds were carefully preserved for the succeeding crop; and, by a constant repetition of this practice for many years, at last the habit to produce a round and succulent root became so fixed, that all the Radishes assumed the same appearance and quality, and there were none left to draft or "rogue." Every variety of annual crop, not still in its wild state, must have gone through this process of fixing; and thus the varieties of earliness, lateness, and productiveness, colour, form, and flavour observable in garden plants, have been secured for our enjoyment.

The following experiment has been recorded by an intelligent observer writing under the name of Lusor:-"If we breed live stock, of whatever kind, we invariably select the parents from the best of our flock or stud. So, with regard to flowers, no one would sow seed from

ORIGIN OF DOMESTICATED CARROTS.

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inferior flowers, but would select from the best specimens; and it is by following up this system (even without more crossing than is performed by Nature, and the bees), that great improvements have been made. Thinking the same effects would accrue from a more careful selection of culinary seeds, and that a much greater degree of productiveness might be attained, about three years ago I began an experiment with long-pod Beans; I carefully selected the finest and fullest pods for seed, taking none with fewer than five Beans in each. Next year I had a good sprinkling of pods with six seeds in each; these were saved for seed. The following year there were many six-seeded pods and some with seven. Following up the same plan, I find this season many more six and seven-seeded pods, than of a less number, and some with eight seeds; there are still a few plants which produce five-seeded pods, and it is worthy of remark, that the five-seeded plants have seldom a sixseeded pod upon them, but all fives; on the contrary, a six-seeded plant generally has nearly all the pods bearing six Beans or more.'

By a similar process M. Vilmorin obtained domesticated Carrots from wild ones in a few generations (Hort. Trans., 2nd ser., vol. ii., p. 348), and the curious experiments of M. Esprit Fabre upon fixing the character of Wheat in plants derived from an Ægilops, were conducted upon the same principles (Journ. Agr. Soc., vol. xv., p. 167). In fact it is thus, and thus only, that in annual plants any improvement in quality can be rendered permanent.

There is a class of facts apparently opposed to these views. It is said that the fruit of Apple and Pear-trees, raised from the seeds of varieties of the highest excellence, will often be little better than that of wildings. This obscure subject will be considered in the next chapter, in connection with hybridity.

But to fix a new habit in annual plants is not the only care of the cultivator, whose patience and skill would be ill employed if it could not be preserved. If a plant has some tendency to vary from its original condition, it has much more to revert to its wild state; and there can be no doubt that, if the arts of cultivation were abandoned for only a very few years, all the annual varieties of our gardens would disappear, and be replaced by a few original wild forms.

For the means of preserving the races of plants pure, the means vary according to the nature of the variety. As far as concerns early and late varieties, it often happens that, as in Peas, the tendency in such plants to advance or retard their season of ripening was originally connected with the soil or climate in which they grew. A plant which for years is

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