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
Mr. J. Scott sent me from India dried flowers of a heterostyled species of this
genus, which is closely allied to the last. The pistil in the long-styled
flowers is longer by about a quarter of its length, and the stamens shorter in
about the same proportion, than the corresponding organs in the short-styled
flowers. In the latter the anthers are longer, and the divergent stigmas
decidedly longer and apparently thinner than in the long-styled form. Owing to
the state of the specimens, I could not decide whether the stigmatic papillae
were longer in the one form than in the other. The pollen-grains, distended with
water, from the short-styled flowers were to those from the long-styled as 100
to 78 in diameter, as deduced from the mean of ten measurements of each kind.
Hedyotis [sp.?] (Rubiaceae).
Fritz Muller sent me from St. Catharina, in Brazil, dried flowers of a small
delicate species, which grows on wet sand near the edges of fresh-water pools.
In the long-styled form the stigma projects above the corolla, and stands on a
level with the projecting anthers of the short-styled form; but in the latter
the stigmas stand rather beneath the level of the anthers in the other or long-
styled form, these being enclosed within the tube of the corolla. The pistil of
the long-styled form is nearly thrice as long as that of the short-styled, or,
speaking strictly, as 100 to 39; and the papillae on the stigma of the former
are broader, in the ratio of 4 to 3, but whether longer than those of the short-
styled, I could not decide. In the short-styled form, the anthers are rather
larger, and the pollen-grains are to those from the long-styled flowers, as 100
to 88 in diameter. Fritz Muller sent me a second, small-sized species, which is
likewise heterostyled.
Coccocypselum [sp.?] (Rubiaceae).
Fritz Muller also sent me dried flowers of this plant from St. Catharina, in
Brazil. The exserted stigma of the long-styled form stands a little above the
level of the exserted anthers of the short-styled form; and the enclosed stigma
of the latter also stands a little above the level of the enclosed anthers in
the long-styled form. The pistil of the long-styled is about twice as long as
that of the short-styled, with its two stigmas considerably longer, more
divergent, and more curled. Fritz Muller informs me that he could detect no
difference in the size of the pollen-grains in the two forms. Nevertheless,
there can be no doubt that this plant is heterostyled.
Lipostoma [sp.?] (Rubiaceae).
Public-domain text, read in full here on John Shaqi.
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