[6] It is to be understood that wherever a given factor is present the plant may be homozygous or heterozygous for it without alteration in its colour.
[7] It should be mentioned that as the shape of the pollen coat, like that of the seed coat, is a maternal character, all the grains of any given plant are either long or else round. The two kinds do not occur together on the same plant.
[8] For the most recent discussion of this peculiar case the reader is referred to Professor Castle's paper in Science, December 16, 1910.
[9] Paradisus Terrestris, London, 1629, p. 261.