In the last two sections we have seen that in using peas of the “grey” class, i.e. with brown, red, or purplish coats, special phenomena are to be looked for, and also that in the case of large “indented” peas, the phenomena of size and shape may show some divergence from that simple form of the phenomenon of dominance seen when ordinary round and wrinkled are crossed. Here the fuller discussion of these phenomena must have been left to await further experiment, were it not that we have other evidence bearing on the same questions. The first is that of Knight’s well-known experiments, long familiar but until now hopelessly mysterious. I have not space to quote the various interpretations which Knight and others have put upon them, but as the Mendelian principle at once gives a complete account of the whole, this is scarcely necessary, though the matter is full of historical interest. Crossing a white pea with a very large grey purple-flowered form Knight (21) found that the peas so produced “were not in any sensible degree different from those afforded by other plants of the same [white] variety; owing, I imagine, to the external covering of the seed (as I have found in other plants) being furnished entirely by the female[99].” All grew very tall[100], and had colours of male parent[101]. The seeds they produced were dark grey[102]. [99] Thus avoiding the error of Seton, see p. 144. There is no xenia perhaps because the seed-coat of mother was a transparent coat. [100] As heterozygotes often do. [101] Dominance of the purple form. [102] Dominance of the grey coat as a maternal character. “I had frequent occasion to observe, in this plant [the hybrid], a stronger tendency to produce purple blossoms, and coloured seeds, than white ones; for when I introduced the farina of a purple blossom into a white one, the whole of the seeds in the succeeding year became coloured [viz. _DR_ × _D_ giving _DD_ and _DR_]; but, when I endeavoured to discharge this colour, by reversing the process, a part only of them afforded plants with white blossoms; this part sometimes occupying one end of the pod, and being at times irregularly intermixed with those which, when sown, retained their colour” [viz. _DR_ × _R_ giving _DR_ and _RR_] (draws conclusions, now obviously erroneous[103]). [103] Sherwood’s view (_J. R. Hort. Soc._ XXII. p. 252) that this was the origin of the “Wrinkled” pea, seems very dubious. In this account we have nothing not readily intelligible in the light of Mendel’s hypothesis.