Nevertheless,
the greater number likewise present structures which are manifestly
adapted, though not in so striking a manner, for self-fertilisation. The
chief of these is their hermaphrodite condition; that is, their
including within the same corolla both the male and female reproductive
organs. These often stand close together and are mature at the same
time; so that pollen from the same flower cannot fail to be deposited at
the proper period on the stigma. There are also various details of
structure adapted for self-fertilisation. (10/19. Hermann Muller 'Die
Befruchtung' etc. page 448.) Such structures are best shown in those
curious cases discovered by Hermann Muller, in which a species exists
under two forms,--one bearing conspicuous flowers fitted for
cross-fertilisation, and the other smaller flowers fitted for
self-fertilisation, with many parts in the latter slightly modified for
this special purpose. (10/20. 'Nature' 1873 pages 44, 433.)
As two objects in most respects opposed, namely, cross-fertilisation and
self-fertilisation, have in many cases to be gained, we can understand
the co-existence in so many flowers of structures which appear at first
sight unnecessarily complex and of an opposed nature. We can thus
understand the great contrast in structure between cleistogene flowers,
which are adapted exclusively for self-fertilisation, and ordinary
flowers on the same plant, which are adapted so as to allow of at least
occasional cross-fertilisation.
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