CHAP. II. CONSIDERED BOTANICALLY. 215 



The subject of species and varieties has, in our opinion, been placed in the 

 clearest light, by Professor De Candolle, in his Theorie E'lementairc, and in 

 his Physiologie Vegctale. In the latter work, this celebrated botanist recog- 

 nises 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 re- 

 semblance to each other, to induce us to believe that they might have origi- 

 nated 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 appear- 

 ance, 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. Veget., 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, notwith- 

 standing the thousands of varieties in cultivation throughout the temperate 

 regions of the world, and the immense difference between some of the varie- 

 ties (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 -Fraxi- 

 nus, U^mxis, <Salix, Quercus, 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 excelsior. 

 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 Salix, Quercus, &c. 



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- 



