6. _Trifolium pratense perenne_, sub-var. _album_—White Perennial Clover.—Not common, but still, like 3, an albino form, and is, perhaps, more delicate in constitution than the coloured sorts. Now, it appears to us that the descendants of the two types, _Trifolium pratense_ and _T. medium_ (see Plate) form the basis of the red or broad-leaved clover on the one hand, and the perennial or cow-grass clover on the other; whilst the market varieties have, perhaps, been modified by climate, soil, and probably hybridization with other sorts. It may, indeed, be that, after all, the plants described in chapter XVII. as two distinct species are only varieties, for though the common form of _T. pratense_ grows everywhere on mixed soils, the more sandy positions, as the sandstones connected with the coal in South Wales, offer a greater abundance of the _T. medium_; and, from experiments conducted with seed of this latter obtained from near Swansea, Glamorgan, and sown on forest marble clay of the Cotteswolds, we certainly obtained plants differing very much from the typical form of _T. medium_, and assuming the usual broad-leaved clover variations. Here, then, is opened up a curious subject for inquiry, which the history of the seed trade as it relates to clover-seed may tend in some measure to elucidate. Some few years ago _T. pratense_ and _T. medium_ were advertised as on sale by most seedsmen; in fact, the latter was the name by which what is now called cow-grass clover was known. Now, however, it is doubtful if any seedsman would pretend to send out the _T. medium_; but the label _T. pratense perenne_ has been substituted for it. Sinclair’s figure of “Trifolium medium, marl-clover, cow-grass,” in the “Hortus Gramineus Woburnensis,” facing page 141, is scarcely a true form of the plant, as its more or less emarginate leaflets incline to the form of _T. pratense_; and yet, at the time this author wrote, even this was doubtful. _T. medium_ was difficult to obtain, as he says, “All the seeds and plants I have had for this (except that from Messrs. Gibbs & Co., which proved to be the present plant—_T. medium_ of Sinclair) have turned out only two-year lived plants, or never exceeding three, though cultivated on various soils.” We have repeatedly written for seed, and ten years ago were always supplied with samples so labelled; but in no case did we get it. Latterly seedsmen honestly confess that they have not the seed, but can send _T. pratense perenne_.