The Effects of Cross & Self-Fertilisation in the Vegetable KingdomDarwin, Charles
Science
The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom
Darwin, Charles
Fertilization of plants; Plants -- Variation; Pollination
were fertilised with pollen from a distinct plant of the Brazilian
stock, and produced eight capsules, containing on an average about
eighty seeds: this gives a ratio of 15 seeds for the self-fertilised
capsules to 100 for the crossed capsules. Later in the season twelve
other flowers on these two plants were artificially self-fertilised; but
they yielded only two capsules, containing three and six seeds. It
appears therefore that a lower temperature than that of Brazil favours
the self-fertility of this plant, whilst a still lower temperature
lessens it. As soon as the two plants which had been covered by the net
were uncovered, they were visited by many bees,and it was interesting to
observe how quickly they became, even the more sterile plant of the two,
covered with young capsules. On the following year eight flowers on
plants of the Brazilian stock of self-fertilised parentage (i.e.,
grandchildren of the plants which grew in Brazil) were again
self-fertilised, and produced five capsules, containing on an average
27.4 seeds, with a maximum in one of forty-two seeds; so that their
self-fertility had evidently increased greatly by being reared for two
generations in England. On the whole we may conclude that plants of the
Brazilian stock are much more self-fertile in this country than in
Brazil, and less so than plants of the English stock in England; so that
the plants of Brazilian parentage retained by inheritance some of their
former sexual constitution. Conversely, seeds from English plants sent
by me to Fritz Muller and grown in Brazil, were much more self-fertile
than his plants which had been cultivated there for several generations;
but he informs me that one of the plants of English parentage which did
not flower the first year, and was thus exposed for two seasons to the
climate of Brazil, proved quite self-sterile, like a Brazilian plant,
showing how quickly the climate had acted on its sexual constitution.
Abutilon darwinii.
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