But the results thus obtained are liable to very great fallacies, unless the experiment is followed out in all its bearings, with many precautions rarely attended to; and what is supposed to furnish irresistible proofs of permanency of character, when inquired into, will often be found to add nothing at all to the arguments derived from observation.
In the first place, it is a very common practice, in thus testing by cultivation the permanency of character in a plant, to remove it bodily to a garden, and there to propagate it by suckers, cuttings, or other modes of division—an experiment which may, indeed, show the immediate effects of soil, climate, or other extraneous influences on the individual—but, as a test of value between species and variety, it can be of no avail. It is the very method adopted by gardeners for perpetuating individual variations. The only mode in which the test can really bear upon the question, is by sowing the seed, and observing the results in future generations. And in this proceeding it is not enough to raise a few plants in one spot, for two or three generations; for such a course would prove our varieties of kitchen-garden annuals to be all distinct species, which we all know is not the fact; the cultivation must be on a large scale, under circumstances of soil, climate, &c., as varied as the plant will bear, and for many generations; and, after all, the proofs of distinctness can scarcely be absolute, for they consist, as it were, in proving a negative. The object is not to show how long a particular form can be made to endure, but that it will always endure, in spite of external influences or other accidents—that it will not vary under any circumstances, or at any time. The cultivation must be that of the gardener, whose object is to raise new varieties—not of the curator, desirous of keeping his botanic garden usefully cropped, and correctly named—still less of the botanist, who seeks to uphold a species he has set up. The former sows extensively in different localities, in order to have the greater chance of accidental aberration; he carefully watches his seedlings as they grow up, and selects his seeds for the next generation from such plants as show the slightest tendency to vary in the wished-for direction. The curator, on the contrary, anxious to keep his types true, if he selects the seed at all, takes it from the most healthy, normal, and characteristic individuals.
To illustrate the very slender grounds upon which botanists of considerable and well-deserved reputation will occasionally adduce the results of cultivation as convincing proofs of specific distinctness, let us select from Grenier and Godron's flora an instance taken from a genus worked up with great care, by one of the most accurate observers of individual varieties and local races, and whose views as to their reception as a species M. Grenier entirely adopts. Under Galium spurium, he says, "Cette espéce se produisant invariablement de graines sans perdre aucun de ses caractères, ne saurait être confondue avec le G. Aparine." To justify so sweeping and positive an assertion, we must suppose that he, or some one on whose exactness he has implicit reliance, has sown in several successive years each of the three varieties he mentions of G. spurium, besides the smaller forms of what he considers the true G.
