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Darwin, Charles, 1809-1882

"The Different Forms of Flowers on Plants of the Same Species"

Asa Gray 'American Journal of
Science' 1865 page 101 and elsewhere as already referred to. Kuhn 'Botanische
Zeitung' 1867 page 67.); but as I have been often deceived by this character
taken alone, it seems to me the more prudent course not to rank any species as
heterostyled, unless we have evidence of more important differences between the
forms, as in the diameter of the pollen-grains, or in the structure of the
stigma. The individuals of many ordinary hermaphrodite plants habitually
fertilise one another, owing to their male and female organs being mature at
different periods, or to the structure of the parts, or to self-sterility, etc.;
and so it is with many hermaphrodite animals, for instance, land-snails or
earth-worms; but in all these cases any one individual can fully fertilise or be
fertilised by any other individual of the same species. This is not so with
heterostyled plants: a long-styled, mid-styled or short-styled plant cannot
fully fertilise or be fertilised by any other individual, but only by one
belonging to another form. Thus the essential character of plants belonging to
the heterostyled class is that the individuals are divided into two or three
bodies, like the males and females of dioecious plants or of the higher animals,
which exist in approximately equal numbers and are adapted for reciprocal
fertilisation.


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