Consequently the
anthers of the latter do not stand on a level with, but rather above the stigmas
of the other form. Differently from what occurs in the following closely allied
genus, Sethia, the stamens are of nearly equal length in the flowers of the same
form. The pollen-grains of the short-styled flowers, measured in their dry
state, are a little larger than those from the long-styled flowers in about the
ratio of 100 to 93. (3/19. F. Muller remarks in his letter to me that the
flowers, of which he carefully examined many specimens, are curiously variable
in the number of their parts: 5 sepals and petals, 10 stamens and 3 pistils are
the prevailing numbers; but the sepals and petals often vary from 5 to 7; the
stamens from 10 to 14, and the pistils from 3 to 4.)
Sethia acuminata (Erythroxylidae).
Mr. Thwaites pointed out several years ago that this plant exists under two
forms, which he designated as forma stylosa et staminea; and the flowers sent to
me by him are clearly heterostyled. (3/20. 'Enumeratio Plantarum Zeylaniae' 1864
page 54.) In the long-styled form the pistil is nearly twice as long, and the
stamens half as long as the corresponding organs in the short-styled form. The
stigmas of the long-styled seem rather smaller than those of the short-styled.
All the stamens in the short-styled flowers are of nearly equal length, whereas
in long-styled they differ in length, being alternately a little longer and
shorter; and this difference in the stamens of the two forms is probably
related, as we shall hereafter see in the case of the short-styled flowers of
Lythrum salicaria, to the manner in which insects can best transport pollen from
the long-styled flowers to the stigmas of the short-styled.
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