CHAP. II. CONSIDERED BOTANICALLY. Q45 
The subject of species and varieties has, in our opinion, been placed in the 
clearest light, by Professor De Candolle, in his Théorie E’lémentaire, and in 
his Physiologie Végétale. 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. Végét., vol. ii. 
. 689. 
: If “i 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 ke 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’lmus, Salix, 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 sufficieat 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 Salix, Quércus, &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- 
