Page:Mendel's principles of heredity; a defence.pdf/91

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in Hybridisation
71

Although in these two experiments likewise some seeds did not germinate, the figures arrived at already in the previous year were not affected thereby, since each kind of seed gave plants which, as regards their seed, were like each other and different from the others. There resulted therefore from the

2nd Exp. 4th Exp.
31 24 plants of the form AaBb
26 25 Aab
27 22 aBb
26 27 ab

In all the experiments, therefore, there appeared all the forms which the proposed theory demands, and also in nearly equal numbers.

In a further experiment the characters of floral colour and length of stem were experimented upon, and selection so made that in the third year of the experiment each character ought to appear in half of all the plants if the above theory were correct. A, B, a, b serve again as indicating the various characters.

A, violet-red flowers. a, white flowers.
B, axis long. b, axis short.

The form Ab was fertilised with ab, which produced the hybrid Aab. Furthermore, aB was also fertilised with ab, whence the hybrid aBb. In the second year, for further fertilisation, the hybrid Aab was used as seed parent, and hybrid aBb as pollen parent.

Seed parent, Aab. Pollen parent, aBb.
Possible egg cells, Abab. Pollen cells, aBab.

From the fertilisation between the possible egg and pollen cells four combinations should result, viz. :—

AaBb + aBb + Aab + ab.