But there are much more
important differences. The stigma in the long-styled form is globular; in the
short-styled it is depressed on the summit, so that the longitudinal axis of the
former is sometimes nearly double that of the latter. Although somewhat variable
in shape, one difference is persistent, namely, in roughness: in some specimens
carefully compared, the papillae which render the stigma rough were in the long-
styled form from twice to thrice as long as in the short-styled. The anthers do
not differ in size in the two forms, which I mention because this is the case
with some heterostyled plants. The most remarkable difference is in the pollen-
grains. I measured with the micrometer many specimens, both dry and wet, taken
from plants growing in different situations, and always found a palpable
difference. The grains distended with water from the short-styled flowers were
about .038 millimetres (10 to 11/7000 of an inch) in diameter, whilst those from
the long-styled were about .0254 millimetres (7/7000 of an inch), which is in
the ratio of 100 to 67. The pollen-grains therefore from the longer stamens of
the short-styled form are plainly larger than those from the shorter stamens of
the long-styled. When examined dry, the smaller grains are seen under a low
power to be more transparent than the larger grains, and apparently in a greater
degree than can be accounted for by their less diameter.
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