Professor de Vries begins by reference to a remarkable memoir by Gregor Mendel[1], giving the results of his experiments in crossing varieties of Pisum sativum. These experiments of Mendel's were carried out on a large scale, his account of them is excellent and complete, and the principles which he was able to deduce from them will certainly play a conspicuous part in all future discussions of evolutionary problems. It is not a little remarkable that Mendel's work should have escaped notice, and been so long forgotten.
For the purposes of his experiments Mendel selected seven pairs of characters as follows:—
1. Shape of ripe seed, whether round; or angular and wrinkled.
2. Colour of "endosperm" (cotyledons), whether some shade of yellow; or a more or less intense green.
3. Colour of the seed-skin, whether various shades of grey and grey-brown; or white.
4. Shape of seed-pod, whether simply inflated; or deeply constricted between the seeds.
5. Colour of unripe pod, whether a shade of green; or bright yellow.
6. Nature of inflorescence, whether the flowers are arranged along the axis of the plant; or are terminal and form a kind of umbel.
7. Length of stem, whether about 6 or 7 ft. long, or about 34 to 112 ft.
Large numbers of crosses were made between Peas differing in respect of one of each of these pairs of characters.
- ↑ 'Versuche üb. Pflanzenhybriden' in the Verh. d. Naturf. Ver. Brünn, iv, 1865.
