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Darwin, Charles, 1809-1882

"The Different Forms of Flowers on Plants of the Same Species"


The solitary almost sessile cleistogamic flowers produced by Monochoria
vaginalis are differently protected from those in any of the previous cases,
namely, within "a short sack formed of the membranous spathe, without any
opening or fissure." There is only a single fertile stamen; the style is almost
obsolete, with the three stigmatic surfaces directed to one side. Both the
perfect and cleistogamic flowers produce seeds. (8/19. Dr. Kirk 'Journal of the
Linnean Society' volume 8 1864 page 147.)
The cleistogamic flowers on some of the Malpighiaceae seem to be more profoundly
modified than those in any of the foregoing genera. According to A. de Jussieu
they are differently situated from the perfect flowers; they contain only a
single stamen, instead of 5 or 6; and it is a strange fact that this particular
stamen is not developed in the perfect flowers of the same species. (8/20.
'Archives du Museum' tome 3 1843 pages 35-38, 82-86, 589, 598.) The style is
absent or rudimentary; and there are only two ovaries instead of three. Thus
these degraded flowers, as Jussieu remarks, "laugh at our classifications, for
the greater number of the characters proper to the species, to the genus, to the
family, to the class disappear." I may add that their calyces are not glandular,
and as, according to Kerner, the fluid secreted by such glands generally serves
to protect the flowers from crawling insects, which steal the nectar without
aiding in their cross-fertilisation (8/21.


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