These cleistogamic
flowers do not differ much in structure from the perfect ones of the
corresponding form, with the exception that their petals are reduced to
extremely minute, barely visible scales, which adhere firmly to the rounded
bases of the shorter stamens. Their stigmas are much less papillose, and smaller
in about the ratio of 13 to 20 divisions of the micrometer, as measured
transversely from apex to apex, than the stigmas of the perfect flowers. The
styles are furrowed longitudinally, and are clothed with simple as well as
glandular hairs, but only in the cleistogamic flowers produced by the long-
styled and mid-styled forms. The anthers of the longer stamens are a little
smaller than the corresponding ones of the perfect flowers, in about the ratio
of 11 to 14. They dehisce properly, but do not appear to contain much pollen.
Many pollen-grains were attached by short tubes to the stigmas; but many others,
still adhering to the anthers, had emitted their tubes to a considerable length,
without having come in contact with the stigmas. Living plants ought to be
examined, as the stigmas, at least of the long-styled form, project beyond the
calyx, and if visited by insects (which, however, is very improbable) might be
fertilised with pollen from a perfect flower. The most singular fact about the
present species is that long-styled cleistogamic flowers are produced by the
long-styled plants, and mid-styled as well as short-styled cleistogamic flowers
by the other two forms; so that there are three kinds of cleistogamic and three
kinds of perfect flowers produced by this one species! Most of the heterostyled
species of Oxalis are more or less sterile, many absolutely so, if
illegitimately fertilised with their own-form pollen.
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