This case resembles that of Linum grandiflorum,
in which the sole difference between the two forms consists in the length of the
pistils and stigmas. From the great length of the tubular corolla of Leucosmia,
it is clear that the flowers are cross-fertilised by large Lepidoptera or by
honey-sucking birds, and the position of the stamens in two whorls one beneath
the other, which is a character that I have not seen in any other heterostyled
dimorphic plant, probably serves to smear the inserted organ thoroughly with
pollen.
Menyanthes trifoliata (Gentianeae).
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.
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