Examples of xenia produced by the contrary proceeding, namely fertilising a yellow pea with a green, may indubitably occur and I have seen doubtful cases; but as by the nature of the case these are _negative_ phenomena, i.e. the seed-coat remaining greenish and _not_ going through its normal maturation changes, they must always be equivocal, and would require special confirmation before other causes were excluded. Lastly, the special change (xenia) Mendel saw in “grey” peas, appearance or increase of purple pigment in the thick coats, following crossing, is common but also irregular. If a _transparent_ coated form be taken as seed-parent there is no appreciable xenia, so far as I know, and such a phenomenon would certainly be paradoxical[82]. [82] In some transparent coats there is pigment, but so little as a rule that xenia would be scarcely noticeable. In this connection it is interesting to observe that Giltay, whom Professor Weldon quotes as having obtained purely Mendelian results, got no xenia though searching for it. If the reader goes carefully through Giltay’s numerous cases, he will find, _almost_ without doubt, that none of them were such as produce it. _Reading Giant_, as Giltay states, has a _transparent_ skin, and the only xenia likely to occur in the other cases would be of the peculiar and uncertain kind seen in using “grey” peas. Professor Weldon notes that Giltay, who evidently worked with extreme care, _peeled_ his seeds before describing them, a course which Professor Weldon, not recognizing the distinction between the varieties with opaque and transparent coats, himself wisely recommends. The coincidence of the peeled seeds giving simple Mendelian results is one which might have alarmed a critic less intrepid than Professor Weldon. Bearing in mind, then, that the coats of peas may be transparent or opaque; and in the latter case may be variously pigmented, green, grey, reddish, purplish, etc.; that in any of the latter cases there may or may not be xenia; the reader will perceive that to use the statements of an author, whether scientific or lay, to the effect that on crossing varieties he obtained peas of such and such colours _without specifying at all whether the coats were transparent or whether the colours he saw were coat- or cotyledon-colours_ is a proceeding fraught with peculiar and special risks. (1) _Gärtner’s cases._ Professor Weldon gives, as exceptions, a series of Gärtner’s observations. Using several varieties, amongst them _Pisum sativum macrospermum_, a “grey” pea, with coloured flowers and seed-coats[83], he obtained results partly Mendelian and partly, as now alleged, contradictory. The latter consist of seeds “dirty yellow” and “yellowish green,” whereas it is suggested they should have been simply yellow. [83] Usually correlated characters, as Mendel knew.