Gregor Mendel

Of the experiments of previous years, those dealing with Matthiola annua and glabra, Zea, and Mirabilis were concluded last year. Their hybrids behave exactly like those of Pisum. Darwin's statements concerning hybrids of the genera mentioned in The variation of animals and plants under domestication, based on reports of others, need to be corrected in many respects.

Letter VIII, July 3rd, 1870. , 1870

Experience of artificial fertilization, such as is effected with ornamental plants in order to obtain new variations in colour, has led to the experiments which will here be discussed. The striking-regularity with which the same hybrid forms always reappeared whenever fertilisation took place between the same species induced further experiments to be undertaken, the object of which was to follow up the developments of the hybrids in their progeny.

[1] Introductory Remarks , 1865

I am inclined to regard the separation of parental traits in the progeny of hybrids in Pisum as complete and thus permanent. The progeny of hybrids carries one or the other of the parental traits, or the hybrid form of the two; I have never observed gradual transitions between the parental traits or a progressive approach towards one of them. The course of development consists simply in this; that in each generation the two parental traits appear, separated and unchanged, and there is nothing to indicate that one of them has either inherited or taken over anything from the other

April 18, 1867. , 1867

It is willingly granted that by cultivation the origination of new varieties is favored, and that by man's labor many varieties are acquired which, under natural conditions, would be lost; but nothing justifies the assumption that the tendency to formation of varieties is so extraordinarily increased that the species speedily lose all stability, and their offspring diverge into an endless series of extremely variable forms. Were the change in the conditions the sole cause of variability we might expect that those cultivated plants which are grown for centuries under almost identical conditions would again attain constancy.

[10] Experiments with Hybrids of Other Species of Plants , 1865

It concerns the opinion of Naudin and Darwin that a single pollen grain does not suffice for fertilization of the ovule. I used Mirabilis Jalappa for an experimental plant, as Naudin had done; the result of my experiment is, however, completely different. From fertilizations with single pollen grains, I obtained eighteen well-developed seeds, and from these an equal number of plants, of which ten are already in bloom

Letter VIII, July 3rd, 1870. , 1870