case of adhesion, that in which the liber, and particularly pith, of two plants unite so nicely together that the part called the graft can receive its sap, and thus live by the nourishment it derives through the organs of the old plant; thus artificially doing what parasitic plants, such as the mistletoe, do by nature. There is, however, a limit to this operation; if we except parasitical and some few natural adhesions, we shall find that artificially it is only plants of the same natural family that can be grafted together with anything like permanent success, and only those of families strongly analogous in which any union will take place at all. When they are not of the same family the grafts are of short duration in consequence of their physiological difference from the tree to which they have been united. Grafts are of three kinds that ordinarily so called, in which a severed portion of a stem is united to another tree, whose bark has been cut away at the proper spot,―that by approach, which consists of drawing two branches or two trees together, each remaining in the ground held by its own roots, and taking off the bark of each at the point of contact; the liber and pith of the two plants soon unite by the development of their cambium, and one of them may then be cut away below the junction. The third method is by the insertion of a portion of a stem containing a bud in the axil of a leaf, within the bark of the tree on which we desire to ingraft it; the bud thus inserted receives nourishment from the juices of the tree in which it is placed, and is developed as it would have been on the stem from which it was originally taken.

76. There are various subjects of great interest connected with the reproduction of plants, whether from seed or division, but which are too numerous

to be dwelt on in an elementary work; among them is the production of hybrid varieties by fertilizing the stigma of one plant with the pollen from another, which may occur accidentally, if the plants are in each other's neighbourhood, or may be effected at pleasure between those whose natural affinities are very close. In this manner modern gardeners have succeeded in raising numberless varieties of favorite genera. The effect of culture and care generally, as is universally known, is to improve the beauty and value of the vegetable productions by which we are so bountifully surrounded. This subject, interesting as it is, can here be only recommended to notice, without further entering on it. Its details may afford to those whose local situation enables them practically to pursue them, an occupation at once healthy to both body and mind, and so connected with chemistry and mineralogy, as to lead on from the simple nurture of a pretty or useful plant, to the study of some of the most important of the sciences.

77. What great antiquity the method of grafting may claim, we may gather from St. Paul's exhortation to the Gentiles in the 11th chapter of his Epistle to the Romans, in which the metaphor is used throughout with an evident knowledge of the subject. Indeed the custom appears to have been one with which practical gardeners have been familiar for ages, and to which attention has been at times particularly turned.

In the Philosophical Transactions for 1675, mention is made of a work by Abraham Munting, printed three years before, which shows that his attention was practically given to the cultivation of fruit trees, and to the improvement of the sorts by grafting. "To obtain extraordinary good, large, and beautiful apple fruit," he advises "by all means to graft good

grafts upon such apple stocks as are produced from the seed, and have been deprived of their heart root which shoots downwards."*

To the invaluable and long continued investigations and experiments of Mr. Andrew Knight, however, and to his acute reasoning on the subject, the present highly improved knowledge of the best method of grafting trees, and of the general nature of the subject, is mainly owing. In a paper published in the Phil. Trans. for 1795, Mr. Knight gives a very interesting account of the experiments which convinced him of the fact, so important in its practical results, that "every cutting taken from the apple, and probably every other tree, will be affected by the state of the parent stock. If that be too young to produce fruit, it will grow with vigor but will not blossom; and if it be too old, it will immediately produce fruit, but will never make a healthy tree, and consequently never answer the intention of the planter." Having suspected that the decay in some trees he had seen recently grafted might be the consequence of the diseased condition of the grafts, Mr. Knight says, "I concluded that if I took scions or buds from trees grafted in the year preceding, I should succeed in propagating any kind I chose. With this view, I inserted some cuttings of the best wood I could find in the old trees, on young stocks raised from seed. I again inserted grafts and buds taken from these on other young stocks, and wishing to get rid of all connection with the old trees, I repeated this six years; each year taking the young shoots from the trees last grafted. Stocks of different kinds were tried, some were double graf

66

*Phil. Trans. abridged, vol. xix. p. 192-3, “ Account of some new books."

ted, others obtained from apple trees which grew from cuttings, and others from the seed of each kind of fruit afterwards inserted on them; I was surprised to find that many of these stocks inherited all the diseases of the parent trees."-Mr. Knight came at last to the conclusion, which subsequent experience has fully confirmed, "that all efforts, to make grafts from old and worn out trees grow, are ineffectual," and that "the durability of the apple and pear may be different in different varieties, but that none of either would vegetate with vigor much, if at all, beyond the life of the parent stock. I am confirmed in this opinion by the books on this subject; of the apples mentioned and described by Parkinson, the names only remain, and those since applied to other kinds now also worn out; but many of Evelyn's still remain (1795), particularly the red streak. This apple, he informs us, was raised from seed by Lord Scudamore in the beginning of the last century. We have many trees of it, but they appear to have been in a state of decay during the last forty years

. . . the durability of the pear is probably something more than double that of the apple." Many of the readers of this paragraph will probably recall to mind the gradual and complete extinction of the unrivaled "Golden Pippin," which has evidently afforded a proof of the truth of Mr. Knight's deductions. His experiments on seedling apples, while the excellence of several of the sorts affords much encouragement to gardeners and landed proprietors to imitate his example, and endeavor to replace by new fruit trees of equal goodness, the kinds whose limit of duration may be pretty nearly guessed, also show the necessity in this, as in most pursuits, of the valuable qualities of patience and perseverance which he must himself have possessed in so great a degree,

since of the seeds he sowed he reckoned that one in a thousand came up which was not a crab, and one in a thousand of these became a good eating apple.

*

78. There is one more subject, connected with reproduction by seed, which is too curious to be passed over; the wonderful tenacity of vegetable life. This, indeed, is shown in the plants themselves in many instances, such as the enormous longevity of some trees, particularly the oak, the yew, and some of foreign growth, but it seems even more extraordinary as it exists in seeds. The latter will remain torpid for many months or even years without injury. Corn grains enclosed in the bandages which envelop the mummies, are said to have occasionally germinated, though most of them seem to have lost their vitality. There is nothing improbable in the fact; but as the Arabs, from whom the mummies are commonly obtained, are in the habit of previously unrolling them in search of coins, &c., it is not always certain that the seeds which have sprouted, were really at first enclosed with the mummies.t

* In the Appendix will be found translated a table given by De Candolle of the presumed age of some celebrated trees. (B.)

+ Carpenter's Veg. Physiol., § 451.