Fagopyrum is dimorphic, and Anagallis collina is non-dimorphic, and
the crossed seedlings of both are in height to the self-fertilised as
100 to 69.
With all European plants, excepting the comparatively rare anemophilous
kinds, the possibility of distinct individuals intercrossing depends on
the visits of insects; and Hermann Muller has proved by his valuable
observations, that large conspicuous flowers are visited much more
frequently and by many more kinds of insects, than are small
inconspicuous flowers. He further remarks that the flowers which are
rarely visited must be capable of self-fertilisation, otherwise they
would quickly become extinct. (10/25. 'Die Befruchtung' etc. page 426.
'Nature' 1873 page 433.) There is, however, some liability to error in
forming a judgment on this head, from the extreme difficulty of
ascertaining whether flowers which are rarely or never visited during
the day (as in the above given case of Fumaria capreolata) are not
visited by small nocturnal Lepidoptera, which are known to be strongly
attracted by sugar. (10/26. In answer to a question by me, the editor of
an entomological journal writes--"The Depressariae, as is notorious to
every collector of Noctuae, come very freely to sugar, and no doubt
naturally visit flowers:" the 'Entomologists' Weekly Intelligencer' 1860
page 103.) The two lists given in the early part of this chapter support
Muller's conclusion that small and inconspicuous flowers are completely
self-fertile: for only eight or nine out of the 125 species in the two
lists come under this head, and all of these were proved to be highly
fertile when insects were excluded.
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