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146 hesitation that I have admitted the specific identity of the Primrose and the Cowslip, although several experimenters are stated to have raised the one from the other. In all cases, proof by cultivation seems to require some confirmation by the observation of wild nature.

With regard to genera and orders, I need not here repeat the views I laid before the Linnean Society on a former occasion ("Journ. Linn. Soc. Bot.," v. ii., p. 31), on the importance of maintaining, for the convenience of language and study, large genera and orders, in preference to breaking them up into small independent ones. But the opinions I have on that and other occasions expressed, that genera, as such, have no independent existence in nature, have been in some measure misunderstood. Far be it from me to deny that groups of species exist in nature, resembling each other more than they do the species of any other group—that some of these groups, consisting of two, three, or any number of species, are in nature distinguished from all others by a number of well-marked characters, or that a single species may be so isolated; whilst others can only be separated by single or un- important or variable characters—that these groups may be collected into groups of a higher order, consisting in like manner of two, three, or any number of smaller ones, similarly distinguished in nature by more or less marked or important characters—that this synthetical process, always following natural indications, may be carried on till we arrive at the two or three great primary divisions of the vegetable kingdom—and that in all the stages very great differences exist in nature in the definiteness of the groups established, and in the relative importance of the characters distinguishing them; but that, generally speaking, the characters of a large group are more important than those which only distinguish its minor subordinates; for on these principles,—on a nice, appreciation of affinities (or calculation of resemblances and differences), and of the importance of characters, as indicated in nature,—depends the whole value of a natural classification. What I meant to assert was, that nature has not assigned everywhere precise definite limits to the groups she has indicated; nor has she fixed upon two stages in the synthetical process more definite than any others, to be marked out, the one for genera, the others for orders. These are often selected and limited, arbitrarily, though necessarily, for the convenience of system, language, and reference. The characters of plants are, indeed, very different in importance; but such differences are relative, not absolute; we cannot say that certain characters are of ordinal importance, whilst certain others are only of tribual, generic, or sectional value. Nor does any one character retain the same importance throughout the vegetable kingdom. There is no test by which we can determine whether two groups formed in different parts of the field of classification are co-equal in value, or whether the one be of a higher grade than the other.

It becomes, therefore, necessary to consider what constitutes the relative importance in characters, how far we can safely be guided by