Herr Bouche's observations are of especial interest, for
he shows that both temperature and the amount of light affect the size of the
corolla; and he gives measurements proving that with some plants the corolla is
diminished by the increasing cold and darkness of the changing season, whilst
with others it is diminished by the increasing heat and light. (8/32. For the
statement by Linnaeus see Mohl in 'Botanische Zeitung' 1863 page 327. Asa Gray
'American Journal of Science' 2nd series volume 39 1865 page 105. Bennett in
'Nature' November 1869 page 11. The Reverend G. Henslow also says 'Gardener's
Chronicle' 1877 page 271, also 'Nature' October 19, 1876 page 543, "that when
the autumn draws on, and habitually in winter for such of our wild flowers as
blossom at that season" the flowers are self-fertilised. On Lysimachia H. Muller
'Nature' September 1873 page 433. Bouche 'Sitzungsbericht der Gesell.
Naturforsch. Freunde' October 1874 page 90.)
The belief that the first step towards flowers being rendered cleistogamic was
due to the conditions to which they were exposed, is supported by the fact of
various plants belonging to this class either not producing their cleistogamic
flowers under certain conditions, or, on the other hand, producing them to the
complete exclusion of the perfect ones. Thus some species of Viola do not bear
cleistogamic flowers when growing on the lowlands or in certain districts.
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