THE

QUARTERLY JOURNAL

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SCIENCE, LITERATURE, AND ART.

Remarks on the Naturalization of Plants in colder Climates. Addressed to the Editor by J. MAC CULLOCH, M.D., F.R.S., &c. &c. In a paper which was inserted in your Journal, respecting the horticulture of tender plants, I had occasion to allude to the possibility, real or supposed, of rendering some, at least, of these more hardy, by raising them from seeds produced in a climate of a lower temperature than their original or natural one. At the same time I thought it right to state, that the opinions of the very learned and able secretary of the Horticultural Society were entirely opposed to this doctrine; opinions, I need not say, combining a weight of experience and authority which demand the greatest deference. I am uncertain whether he has himself published those opinions, but as the purpose of this slight communication is to pursue an amicable investigation, not a controversy, with the aid of those who may feel an interest in it, I am sure I cannot offend him by saying, that I have found those opinions, in a personal discussion of this point, at least as decided as I have here stated them. He will doubtless have the kindness to correct me in the same manner, if I am wrong; and will understand that the object of this publicity is the hope of exciting the attention, on whichever side, of those who have the desire and the means of bringing to the test of sufficient experiments what is a matter of pure experiment, and must finally be settled by experience. Like thousands more, I wish that the doctrine were true, or that it may ultimately be proved true; but, like all else in

APRIL-JUNE, 1829.

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science, though too often overlooked in discussion, there can be as little pleasure as advantage in persuading others to receive error as truth, to adopt in this case as a fact that which, whatever value it may possess as one, would lead only to disappointment and evil, should it prove unfounded. And it is one of the most interesting questions in the philosophy of botany, whether in the relations of that science to agriculture or to horticulture, and to the endless modes in which these arts ramify and bear on human life. To assume such a power hypothetically, we see at a glance the enormous revolution it might produce in the present distribution of the vegetable world, and the extensive and valuable consequences that would result from it. To prove that the permanent alteration of the habits of plants, as to climate, is possible, even to a limited extent, would lay the foundation of many advantages, on which it would be as easy as it is unnecessary here to speculate. The extension and the greater economy of ornamental horticulture are obvious contingent results, of no small importance; and yet these would be of little moment, compared to the directly useful consequences in the naturalization of new products in agriculture, or, generally, in augmenting or varying the useful produce of the soil in a given country and climate.

Yet this question, practical as it is interesting, and a source even of entertainment, in whatever way it is finally decided, has scarcely received the slightest attention-none, it may almost be said, compared to its importance, whether as a question of botanical philosophy or utility, to its facility as an object of experiment, and to the amusement it is capable of affording. That also it must be a work of time, and may demand the continued trials of perhaps more than one generation of man, is an additional reason for thus urging it on the public attention, even where that which I have to offer directly on the total question is so extremely slender. But this paper is not meant as a contribution; it is intended merely as a stimulus to inquiry; and should it produce this effect, its end is answered. On the general question of naturalizing the plants of warmer climates in colder ones, through the intervention of their seeds and through successive generations of those, I am fully aware that the fact was too generally assumed, at first, from two

instances; and it may not be untrue that both of the most remarkable examples originally adduced as proofs were fallacious, or at least partially so. The one was the naturalization, real or supposed, of the Zizania aquatica by Sir Joseph Banks, and the other was that of the Canna indica in Guernsey, as noticed by myself. And, on my own part, I am quite willing to admit that the same error may pervade the other examples which I have noticed in the paper to which I have here referred in your Journal. It is unquestionable that, without reference to elevation, that great modifier of climate as constituted by latitude; without reference, in fact, to any external circumstances, there are, in any given climate, native indigenous genera, and species also, which are constitutionally more hardy than their immediate neighbours, and thus capable of bearing considerable changes of climate with impunity, where others, without any apparent reason that we can discover, fail. Such is the case, for example, with the very canna in question, compared to ginger or to the sensitive plant; while the cassia offers another familiar example of extreme susceptibility and repugnance to change, out of a crowd of plants from the same situations which we can cultivate without difficulty. The extent of the range of temperature occupied by the vine, by wheat, and by many more plants that I need not enumerate, shew that on this point there is great variety of susceptibility or hardiness in the vegetable creation; and a variety, of which advantages have been taken, and that may probably be far more widely extended hereafter. And this, in fact, forms one of the important parts of this very question, as it is one that has been neglected, a point to which I shall recur immediately.

In the meantime, to pursue the remarks on the two erroneous conclusions above noticed, it is as unreasonable as it is inconsistent with experimental philosophy, to reject the whole hypothesis, if it really be an hypothesis, on account of those. The vast extent of the subject demands a far wider range of trial; and if two, or twenty, such experiments have failed to establish its truth, neither are they sufficient to prove its falsehood. It is a question that demands, not simply more investigation, but investigation; nor will philosophy act justly in

rejecting an even plausible hypothesis without more trials; it will be far, indeed, from right in ceasing from its investigation, if I can now shew, as I hope to do, some further reasons and some further facts, indicating that the opinion is not so utterly hypothetical as its opponents seem to esteem it. nady a to

As a priori ground of reasoning towards the recommendation of a sufficient course of experiments on this subject, the naturalization of tender plants, I may commence by pointing out the important fact just stated, namely, the great inequality of constitution in different plants which are natives of the same precise climate; of plants which, on a general or superficial view, we should reject or condemn to the house or stové. And this piece of knowledge is but recent, while, being recent, it is also limited as to the number of plants of which it has taken cognizance. There is no gardener now who does not know how many plants he has turned from the stove into the green-house; how many from the green-house into the garden or shrubbery, within these twenty, ten, five years; how many, indeed, are almost annually undergoing this migration, including plants of which, before those trials, he would not have believed in the hardiness. And yet the same fears or hesitation continue, while perhaps not a year passes in which many are not added to those which have undergone this change, a change no less agreeable to us than productive of unforeseen vigour and luxuriance in the plants themselves. I cannot, for one, forget that when first I knew Scotland, there was not a plant but the most rude and hardy attempted to be cultivated, or even ol placed for a summer, in the open ground; that I first pointed out myself those tenderer plants which I believed capable of enduring that climate out of doors, and that I now see everywhere flourishing in the borders the most luxuriant plants of heliotrope, fuchsia, verbena triphylla, geraniums, and numerous others, replacing the wretched, starved specimens formerly nursed with the greatest anxiety in greenhouses. I

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Here, then, is the first ground of trial. We do not yet know what plants out of the hotter climates of the whole world will bear our climate, and it is certain that without trial we never shall know. Nor do we know in what their peculiar delicacy of constitution consists; what are their antipathies; what the