The Different Forms of Flowers on Plants of the Same SpeciesDarwin, Charles
Science
The Different Forms of Flowers on Plants of the Same Species
Darwin, Charles
Fertilization of plants; Heterostylism; Plant physiology; Plants -- Variation; Pollination
The seeds from the great-great-grandchildren were sown, and 8 long-styled and 2
short-styled plants of the fifth illegitimate generation raised. These whilst
still in the greenhouse produced smaller leaves and shorter flower-stalks than
some legitimate plants with which they grew in competition; but it should be
observed that the latter were the product of a cross with a fresh stock,--a
circumstance which by itself would have added much to their vigour. (5/11. For
full details of this experiment, see my ‘Effects of Cross and Self-
fertilisation’ 1876 page 220.) When these illegitimate plants were transferred
to fairly good soil out of doors, they became during the two following years
much more dwarfed in stature and produced very few flower-stems; and although
they must have been legitimately fertilised by insects, they yielded capsules,
compared with those produced by the surrounding legitimate plants, in the ratio
only of 5 to 100! It is therefore certain that illegitimate fertilisation,
continued during successive generations, affects the powers of growth and
fertility of P. veris to an extraordinary degree; more especially when the
plants are exposed to ordinary conditions of life, instead of being protected in
a greenhouse.
[EQUAL-STYLED RED VARIETY OF Primula veris.
Mr. Scott has described a plant of this kind growing in the Botanic Garden of
Edinburgh. (5/12. ‘Proceedings of the Linnean Society’ volume 8 1864 page 105.)
He states that it was highly self-fertile, although insects were excluded; and
he explains this fact by showing, first, that the anthers and stigma are in
close apposition, and that the stamens in length, position and size of their
pollen-grains resemble those of the short-styled form, whilst the pistil
resembles that of the long-styled form both in length and in the structure of
the stigma. Hence the self-union of this variety is, in fact, a legitimate
union, and consequently is highly fertile. Mr. Scott further states that this
variety yielded very few seeds when fertilised by either the long- or short-
styled common cowslip, and, again, that both forms of the latter, when
fertilised by the equal-styled variety, likewise produced very few seeds. But
his experiments with the cowslip were few, and my results do not confirm his in
any uniform manner.
Public-domain text, read in full here on John Shaqi.
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