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
All the fifty-six plants in these three lots proved long-styled; now, if the
parent-plants had been legitimately fertilised by pollen from the longest
stamens of the mid-styled and short-styled forms, only about one-third of the
seedlings would have been long-styled, the other two-thirds being mid-styled and
short-styled. In some other trimorphic and dimorphic genera we shall find the
same curious fact, namely, that the long-styled form, fertilised illegitimately
by its own-form pollen, produces almost exclusively long-styled seedlings. (5/1.
Hildebrand first called attention to this fact in the case of Primula Sinensis
(‘Botanische Zeitung’ January 1, 1864 page 5); but his results were not nearly
so uniform as mine.)
The eight plants of the first lot were of low stature: three which I measured
attained, when fully grown, the heights of only 28, 29, and 47 inches; whilst
legitimate plants growing close by were double this height, one being 77 inches.
They all betrayed in their general appearance a weak constitution; they flowered
rather later in the season, and at a later age than ordinary plants. Some did
not flower every year; and one plant, behaving in an unprecedented manner, did
not flower until three years old. In the two other lots none of the plants grew
quite to their full and proper height, as could at once be seen by comparing
them with the adjoining rows of legitimate plants. In several plants in all
three lots, many of the anthers were either shrivelled or contained brown and
tough, or pulpy matter, without any good pollen-grains, and they never shed
their contents; they were in the state designated by Gartner as contabescent,
which term I will for the future use. (5/2. ‘Beitrage zur Kenntniss der
Befruchtung’ 1844 page 116.) In one flower all the anthers were contabescent
excepting two which appeared to the naked eye sound; but under the microscope
about two-thirds of the pollen-grains were seen to be small and shrivelled. In
another plant, in which all the anthers appeared sound, many of the pollen-
grains were shrivelled and of unequal sizes. I counted the seeds produced by
seven plants (1 to 7) in the first lot of eight plants, probably the product of
parents fertilised by their own-form shortest stamens, and the seeds produced by
three plants in the other two lots, almost certainly the product of parents
fertilised by their own-form mid-length stamens.
[PLANT 1.
Public-domain text, read in full here on John Shaqi.
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