Note 107 — A DEFENCE OF MENDEL’S PRINCIPLES OF HEREDITY.

Here we see dominance of the pigmented seed-coat as a maternal character over white seed-coat. The colours of the seed-coats are described as essentially two: maple or brown-streaked, and violet, the latter being a small minority. As the sequel shows, the latter are heterozygotes, not breeding true. Now Mendel found, and the fact has been confirmed both by Correns and myself, that crossing a grey pea which is capable of producing purple leads to such production as a form of xenia.

We have here therefore in the purple seeds the union of dissimilar gametes, with production of xenia. But as the brown-streaked seeds are also in part heterozygous, the splitting of a compound allelomorph has probably taken place, though without precise statistics and allotment of offspring among the several seeds the point is uncertain. The colour of seed-coats in “grey” peas and probably “maples” also is, as was stated on p. 150, sensitive to conditions, but the whole difference between “maples” and purple is too much to attribute safely to such irregularity. “Maple” is the word used to describe certain seed-coats which are pigmented with intricate brown mottlings on a paler buff ground. In French they are perdrix.