Darwinism stated by Darwin himself / Characteristic passages from the writings of Charles Darwin

by Charles Darwin

CAUSES OF STERILITY AMONG PLANTS.

The Different Forms of Flower,
page 345.

If the sexual elements belonging to the same form are united, the union is an illegitimate one, and more or less sterile. With dimorphic species two illegitimate unions, and with trimorphic species twelve are possible. There is reason to believe that the sterility of these unions has not been specially acquired, but follows as an incidental result from the sexual elements of the two or three forms having been adapted to act on one another in a particular manner, so that any other kind of union is inefficient, like that between distinct species. Another and still more remarkable incidental result is that the seedlings from an illegitimate union are often dwarfed and more or less completely barren, like hybrids from the union of two widely distinct species.