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
This plant inhabits marshes: my son William gathered 247 flowers from so many
distinct plants, and of these 110 were long-styled, and 137 short-styled. The
pistil of the long-styled form is in length to that of the short-styled in the
ratio of about 3 to 2. The stigma of the former, as my son observed, is
decidedly larger than that of the short-styled; but in both forms it varies much
in size. The stamens of the short-styled are almost double the length of those
of the long-styled; so that their anthers stand rather above the level of the
stigma of the long-styled form. The anthers also vary much in size, but seem
often to be of larger size in the short-styled flowers. My son made with the
camera many drawings of the pollen-grains, and those from the short-styled
flowers were in diameter in nearly the ratio of 100 to 84 to those from the
long-styled flowers. I know nothing about the capacity for fertilisation in the
two forms; but short-styled plants, living by themselves in the gardens at Kew,
have produced an abundance of capsules, yet the seeds have never germinated; and
this looks as if the short-styled form was sterile with its own pollen.
Limnanthemum Indicum (Gentianeae).
This plant is mentioned by Mr. Thwaites in his Enumeration of the Plants of
Ceylon as presenting two forms; and he was so kind as to send me specimens
preserved in spirits. The pistil of the long-styled form is nearly thrice as
long (i.e. as 14 to 5) as that of the short-styled, and is very much thinner in
the ratio of about 3 to 5. The foliaceous stigma is more expanded, and twice as
large as that of the short-styled form. In the latter the stamens are about
twice as long as those of the long-styled, and their anthers are larger in the
ratio of 100 to 70. The pollen-grains, after having been long kept in spirits,
were of the same shape and size in both forms. The ovules, according to Mr.
Thwaites, are equally numerous (namely from 70 to 80) in the two forms.
Villarsia [sp.?] (Gentianeae).
Public-domain text, read in full here on John Shaqi.
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