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tree, because along with the young tree of the same species will always be found the botanical specimens. These full-grown trees have, in every instance, been drawn in the autumn, when the leaves were ready to drop off, at which season alone they have their most forcible character. Some further observations on the subject of drawing trees will be found in the Gardener's Magazine, vol. xi. p. 395. to p. 412.; and whoever wishes to become master of the subject will consult the excellent work of Harding already referred to.

CHAP. II.

TREES AND SHRUBS CONSIDERED BOTANICALLY.

THE purpose for which we propose to glance at the study of trees and shrubs, botanically, or as organised beings, is, to explain our reasons for the arrangement which we have adopted in placing them together; for distinguishing between species and varieties; and for the scientific descriptions which we have adopted. It must be evident to the reader, that, before any use can be made of the history of any tree or shrub, means must be devised for distinguishing what particular tree or shrub is meant. From the want of these means, or the ignorance in this branch of knowledge of travellers, many of their remarks on trees, and other organised objects, are of little use because it is impossible for botanists to ascertain, from their descriptions or names, to what species of tree or shrub these names or descriptions apply. There can be no doubt that the difficulties in this respect are much greater when applied to the whole vegetable kingdom, than when they are limited to trees and shrubs; and more especially when they are limited to the trees and shrubs supposed to be actually growing in Britain. But even among these, which, probably, do not greatly exceed 1500, there is, at pre-' sent, the greatest uncertainty in the application of names. In genera consisting of many species, there are scarcely two of the London nurseries where the same names are applied to the same things; and what in one nursery is considered as a variety is, in many cases, elevated in other nurseries to the rank of a species. Hence it becomes necessary, in a work like the present, not only to give our reasons for the classification which we have followed, but also for the specific distinctions which we have drawn, and for the kind of descriptions and figures which we have adopted. These reasons will form the subject of three separate sections.

SECT. I. Of the Classification of Trees and Shrubs.

MOST authors who have hitherto produced works treating exclusively of trees and shrubs, from Evelyn and Du Hamel to the present time, have arranged them in the order of the alphabet. As we have, on various occasions (see Encyc. of Gard., edit. 1835, pref.), given our objections to this mode of arrangement in any work having pretensions to be scientific, and also shown that all the advantages of an alphabetical arrangement, in the body of a work of any greater extent than a pocket dictionary, may be obtained by an alphabetical index, we shall not farther insist on the subject here; neither is it necessary for us to offer any arguments in favour of the arrangement which we have adopted, which is that of the natural system, now so generally preferred, by botanists and scientific cultivators, before all others. It may suffice to say, in favour of this system, that by grouping together objects which resemble one another in the greatest number of particulars, and which are also most alike in their qualities, every thing which is known respecting the properties, uses, or culture of any one of them, may be inferred, in a great measure, of every individual in the whole group. Hence, in the case

of trees and shrubs, or of any description of natural object arranged in this way, however much the names of the objects may in future be changed, the descriptions of the objects will always be found associated together in the same group, or in groups nearly adjoining. Hence, also, when a plant is received, the name of which is unknown, its nature may be anticipated, by observing its resemblance to some group already known.

It is a common opinion among those who know little of scientific botany, that the natural system is only adapted to those who intend to become profound in the science; and that for practical men, and for amateurs, who merely aspire to a slight degree of knowledge, the Linnæan system is the best. There never was a greater mistake. To become master of the natural system requires, indeed, much study and perseverance; but the possession of such a degree of knowledge of it as shall be of far greater use to the cultivator, to the medical man, to the traveller, and to the amateur, than the most profound knowledge of the Linnæan system, may be easily acquired by any person of ordinary capacity. In fact, every child who is in the habit of seeing a great many trees, shrubs, and plants, though he does not know a single botanical name, may be said to understand, to a certain extent, the natural system; because, to preserve order in his ideas, and to assist his memory, he is obliged to throw all the conspicuous plants that come before him into groups palpably distinct. He would thus form the three grand classes of trees, shrubs, and herbaceous plants; and among the trees he would readily distinguish, and group together in his mind, the broadleaved and the fir-leaved, the deciduous and the evergreen, the fruit-bearing and the barren. Among herbaceous plants, he would distinguish the grasses as an obviously distinct class; the bulbous flowers as another, and so on. These divisions, so far as they go, are made on the same principles as the natural system; that is, things are brought together, or called by one common name, on account of their general resemblance; that general resemblance comprehending the whole botanical science of the individuals drawing the distinction. All the difference, therefore, between the natural system of the most learned botanist, and that of the most ignorant country labourer, consists in the former having gone more profoundly into the subject; and having his knowledge founded on principles deduced from the facts accumulated by his predecessors, and not merely on personal experience. In short, all sciences not purely abstract are founded on some simple instinct of our nature, which is perceptible in the customs, not only of ignorant persons in civilised society, but of the rudest savages.

We shall not longer occupy our time in contrasting the advantages of a natural arrangement in describing trees and shrubs, either with an alphabetical one, or with the system of Linnæus, or any other artificial system.

SECT. II. Of the Distinction between Species and Varieties in Trees and Shrubs.

THIS is an intricate subject; and it is one which we are well aware we shall not be able to treat in a manner that will be satisfactory to all our readers. The reason of this is to be found in the difficulty of determining what are species, or natural and permanent forms; and what forms are accidental, or the result of culture, soil, situation, disease, &c., or of cross fecundation; and because the present disposition of botanists seems to be to multiply species rather than to diminish their number.

When we look into a modern catalogue of plants, we are astonished, and almost confounded, by the great number of specific names which are ranked under one generic name. If we endeavour, by inspecting the names more particularly, to discover any relationship between them, we are utterly at a loss. One name is, perhaps, an adjective denoting colour, or some other property belonging to the plant, another indicates the native country of the species; and a third shows that it has been named in commemoration of

some place, or of some individual. If we look at the column, in such catalogues, which indicates the native country of the species, the difficulty is increased rather than lessened: perhaps a native of the tropics is placed next a plant from the frigid zone. In this, as in similar cases of collecting knowledge, the first step is to accumulate facts, and the second is to generalise on them. Hitherto it would appear, that, as far as regards species and varieties, the great object of botanists has been to increase their number, without much regard to grouping them according to their relationship. It is not for us even to try to remedy this evil in respect to all the species and varieties of plants; but we propose to attempt to do so, in as far as respects the hardy trees and shrubs of Britain. We shall notice, in succession, the subjects of species, races, varieties, and variations; and we shall then offer some remarks on mules, hybrids, and what are called botanical species.

A species is defined, by Dr. Lindley, to be" a union of individuals agreeing with each other in all essential characters of vegetation and fructification; capable of reproduction by seed, without change; breeding freely together, and producing perfect seed, from which a fertile progeny can be reared." (Introd. to Bot., p. 365.) This, we believe, is the general definition of a species by botanists; but it evidently requires some modification; for, in the case of many cultivated annual plants, the variety or race is reproduced from seed; and, consequently, if reproduction from seed were considered as a certain test, red, white, woolly-eared, and smooth-chaffed wheat, would be so many distinct species; as would the different varieties of cabbage, turnip, common lupine, &c. In like manner, also, the different varieties of particular species of cultivated fruit trees, might be deemed species; for it is certain that seedlings from such varieties of fruit trees, when no cross fecundation has been effected, always bear a nearer resemblance to the variety which produced the seeds, than to any other variety, or to the original species. The truth we believe to be, that trees and shrubs are subjected to the same law, in regard to the reproduction of varieties from seed, as annual plants; though, from the varieties of the former seldomer falling under our observation, and requiring a longer time to come to maturity, we have not the same opportunity of becoming sufficiently impressed with the identities of their natures as to be able to generalise on them. On examining a number of individual trees or shrubs, raised from seed (say, for example, oaks in an oak wood, or hawthorns in a hedge which has not been cut), we shall not find two individuals exactly alike, either in foliage, in flower, in fruit, in mode of growth, or even in the earliness or lateness of budding, flowering, ripening the fruit, or dropping the leaves. We have no doubt, reasoning from the analogy of the wheat, that, if the acorns or haws of any marked variety in such a wood or hedge as that mentioned were sown, and the plants reared to maturity, they would be found (unless cross fecundation had been accidentally or artificially effected) more like the parent variety than any other in the wood or hedge, just as in the case of seedlings from varieties of wheat, cabbage, or fruit trees.

These may be called cultivated varieties, or, according to De Candolle, races; but there are others, which we shall call accidental varieties that we are not so certain can be continued by seed. For example, there are weeping varieties of certain trees, such as the common ash; and fastigiate varieties of others, such as the Exeter elm, the Crataegus Oxyacántha stricta, and the Lombardy poplar (P. fastigiàta), which we believe to be only an accidental variety of P. nìgra: these varieties, we think, would scarcely come true from seed in every, or even in many, cases; though we have no doubt they would in some. Variegated trees and shrubs, we should suppose, would not always come true from seed, any more than variegated annuals or bulbs; but we have no doubt that, as in the two latter cases, a certain proportion of the progeny would be variegated in trees and shrubs, as well as in herbaceous plants. The raising of seedlings from such accidental varieties then, will prove that they are not entitled to rank with cultivated varieties or races.

The difficulty of being able to determine what is only a variety, and what may be ranked as a species, is ably pointed out by Dr. Lindley, in the following passage:- “The manner in which individuals agree in their external characters is the only guide which can be followed in the greater part of plants. We do not often possess the means of ascertaining what the effect of sowing the seed or mixing the pollen of individuals would be; and, consequently, this test, which is the only sure one, is, in practice, seldom capable of being applied. The determination of what is a species, and what a variety, becomes, therefore, wholly dependent npon external characters, the power of duly appreciating which, as indicative of specific difference, is only to be obtained by experience, and is, in all cases, to a certain degree, arbitrary. It is probable that, in the beginning, species only were formed; and that they have, since the creation, sported into varieties, by which the limits of the species themselves have now become greatly confounded. For example, it may be supposed that a rose, or a few species of rose, were originally created. In the course of time these have produced endless varieties, some of which, depending for a long series of ages upon permanent peculiarities of soil or climate, have been in a manner fixed, acquiring a constitution and physiognomy of their own. Such supposed varieties have again intermixed with each other, producing other forms, and so the operation has proceeded. But, as it is impossible, at the present day, to determine which was the original, or originals, from which all the roses of our own time have proceeded, or even whether they were produced in the manner I have assumed; and, as the forms into which they divide are so peculiar as to render a classification of them indispensable to accuracy of language; it has become necessary to give names to certain of those forms which are called species." (Ibid. p. 366.) The secret of the great number of names of species which at present form the bulk of names in our catalogues is to be found in what follows from the same author: "Thus it seems that there are two sorts of species: the one, called natural species, determined by the definition given above; and the other, called botanical species, depending only upon the external characters of the plant. The former have been ascertained to a very limited extent: of the latter nearly the whole of systematic botany consists. In this sense a species may be defined to be an assemblage of individuals agreeing in all the essential characters of vegetation and fructification.'" (Ibid., p.366.)

The difficulty of determining what is a species, and what is a variety, as far as concerns plants of culture, may here be considered as diminished; but, since it is acknowledged by Dr. Lindley, that nearly the whole of systematic botany consists of what are called "botanical species, depending only upon the external characters of the plant," the idea of determining, with any thing like absolute certainty, what is a species, at least a botanical species, and what is a variety, seems almost hopeless. The "whole question," Dr. Lindley observes," lies with the word essential. What is an essential character of a species? This will generally depend upon a proneness to vary, or to be constant in particular characters, so that one class of characters may be essential in one genus, another class in another genus; and these points can be only determined by experience. Thus, in the genus Dahlia, the form of the leaves is found to be subject to great variation; the same species producing, from seed, individuals, the forms of whose leaves vary in a very striking manner the form of the leaves is, therefore, in Dahlia, not a specific character. In like manner, in Rosa, the number of prickles, the surface of the fruit, or the surface of the leaves, and their serratures, are found to be generally fluctuating characters, and cannot often be taken as essential to species. The determination of species is, therefore, in all respects, arbitrary, and must depend upon the discretion or experience of the botanist. It may, nevertheless, be remarked, that decided differences in the forms of leaves, iu the figure of the stem, in the surface of the different parts, in the inflorescence, in the proportion of parts, or in the form of the sepals and petals, usually constitute good specific differences." (Ibid., p. 366, 367.)

The subject of species and varieties has, in our opinion, been placed in the clearest light, by Professor De Candolle, in his Théorie Elémentaire, and in his Physiologie Végétale. In the latter work, this celebrated botanist recognises in plants-species, races, varieties, and variations.

Species. Under the name of species, that is what we consider aboriginal species in contradistinction to the botanical species of botanists, Professor De Candolle unites all those individuals which bear a sufficient degree of resemblance to each other, to induce us to believe that they might have originated in one being, or one pair of beings. The degree of resemblance which authorises us to unite individuals under the denomination of a species varies much in different families; and it often happens that two individuals which really belong to the same species differ more between themselves in appearance, than others which are of distinct species: thus, the spaniel and the Danish dog are externally more different from each other than the dog and the wolf are; and many of the varieties of our fruit trees offer more apparent differences than are found between many species. (Physiol. Végét., vol. ii. p. 689.)

If all the alleged species and varieties of any tree, shrub, or plant were collected together, and cultivated in the same garden, however numerous were the varieties, and however remote they might appear to be from the original species, it would be practicable, after a series of years, to decide with absolute certainty what were aboriginal or fixed features, and what features were variable. For example, in the case of the apple, notwithstanding the thousands of varieties in cultivation throughout the temperate regions of the world, and the immense difference between some of the varieties (for example, the Alexander or the Hawthornden and the original crab), and even the great difference between the crabs of different parts of Europe, yet in no case is there any danger of one of these varieties being mistaken for a pear. One general character of leaf, flower, and fruit is common to the whole of them, though it may not be easy to define in what this essential character consists, in such a manner as to render it observable to any one who had not seen a great number of varieties of apples and crabs. Again, in the case of the common hawthorn, though some of the varieties have deep red fruit, others pale red fruit, others yellow, and others black fruit; and though some varieties of hawthorn have drooping branches, and others have them rigidly erect and fastigiate; though some have the leaves finely cut, and others obtusely lobed or scarcely lobed at all; though some are polygynous, and some are monogynous; yet there never can be any difficulty, when all these varieties are before us, in determining that they belong to one and the same species. The same observation will apply to the numerous varieties of the cockspur thorn, which now figure in our catalogues as distinct species; and we think that it might be applied to many varieties of the genera Fráxinus, Ulmus, Sàlix, Quércus, Pinus, and to various others. Could we bring before us, into one plantation, all those ashes which are natives of America, and watch them for a sufficient number of years, we have no doubt that we should not find it more difficult to assign them to one species, than we do the different varieties of the European ash to the Fraxinus excélsior. All the elms of Europe, we are inclined to be of opinion, may be reduced to only three species; and we much question if, on De Candolle's principle of determining what a species is, there would be more than a tithe of the names which are ranked as such under Sàlix, Quércus, &c.

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Races.- A race in the vegetable, as in the animal, kingdom, De Candolle observes, "is such a modification of the species, whether produced by exterior causes, or by cross fecundation, as can be transmitted from one generation to another by seed." Thus, among all the cultivated vegetables and fruits, both of the garden and of the field, the greater number of sorts may be considered as races, because they may all be continued by seed; the culture given and other circumstances being the same. If the culture were neglected for a series of generations, there can be no doubt that the race would revert to the abori

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