Although cleistogamic flowers never fail to yield a large number of seeds, yet
the plants bearing them usually produce perfect flowers, either simultaneously
or more commonly at a different period; and these are adapted for or admit of
cross-fertilisation. From the cases given of the two Indian species of Viola,
which produced in this country during several years only cleistogamic flowers,
and of the numerous plants of Vandellia and of some plants of Ononis which
behaved during one whole season in the same manner, it appears rash to infer
from such cases as that of Salvia cleistogama not having produced perfect
flowers during five years in Germany (8/31. Dr. Ascherson 'Botanische Zeitung'
1871 page 555.), and of an Aspicarpa not having done so during several years in
Paris, that these plants would not bear perfect flowers in their native homes.
Von Mohl and several other botanists have repeatedly insisted that as a general
rule the perfect flowers produced by cleistogamic plants are sterile; but it has
been shown under the head of the several species that this is not the case. The
perfect flowers Viola are indeed sterile unless they are visited by bees; but
when thus visited they yield the full number of seeds. As far as I have been
able to discover there is only one absolute exception to the rule that the
perfect flowers are fertile, namely, that of Voandzeia; and in this case we
should remember that cultivation often affects injuriously the reproductive
organs.
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