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
As any variation in the structure of the reproductive organs, combined with
changed function, is a rare event, the following cases are worth giving in
detail. My attention was first called to the subject by observing, in 1862, a
long-styled plant, descended from a self-fertilised long-styled parent, which
had some of its flowers in an anomalous state, namely, with the stamens placed
low down in the corolla as in the ordinary long-styled form, but with the
pistils so short that the stigmas stood on a level with the anthers. These
stigmas were nearly as globular and as smooth as in the short-styled form,
instead of being elongated and rough as in the long-styled form. Here, then, we
have combined in the same flower, the short stamens of the long-styled form with
a pistil closely resembling that of the short-styled form. But the structure
varied much even on the same umbel: for in two flowers the pistil was
intermediate in length between that of the long and that of the short-styled
form, with the stigma elongated as in the former, and smooth as in the latter;
and in three other flowers the structure was in all respects like that of the
long-styled form. These modifications appeared to me so remarkable that I
fertilised eight of the flowers with their own pollen, and obtained five
capsules, which contained on an average 43 seeds; and this number shows that the
flowers had become abnormally fertile in comparison with those of ordinary long-
styled plants when self-fertilised. I was thus led to examine the plants in
several small collections, and the result showed that the equal-styled variety
was not rare.
TABLE 5.31. Primula Sinensis. Preponderance of long-styled over the short-styled
form.
Column 1: Name of owner or place.
Column 2: Long-styled form.
Column 3: Short-styled form.
Column 4: equal-styled variety.
Mr. Horwood : 0 : 0 : 17.
Mr. Duck : 20 : 0 : 9.
Baston : 30 : 18 : 15.
Chichester : 12 : 9 : 2.
Holwood : 42 : 12 : 0.
High Elms : 16 : 0 : 0.
Westerham : 1 : 5 : 0.
My own plants from purchased seeds : 13 : 7 : 0.
Total : 134 : 51 : 43.
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