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
Seeds of this plant were sent me by Fritz Muller, who found it, as well
as some other species of the same genus, quite sterile in its native
home of South Brazil, unless fertilised with pollen from a distinct
plant, either artificially or naturally by humming-birds. (9/9.
‘Jenaische Zeitschr. fur Naturwiss’ B. 7 1872 page 22 and 1873 page
441.) Several plants were raised from these seeds and kept in the
hothouse. They produced flowers very early in the spring, and twenty of
them were fertilised, some with pollen from the same flower, and some
with pollen from other flowers on the same plants; but not a single
capsule was thus produced, yet the stigmas twenty-seven hours after the
application of the pollen were penetrated by the pollen-tubes. At the
same time nineteen flowers were crossed with pollen from a distinct
plant, and these produced thirteen capsules, all abounding with fine
seeds. A greater number of capsules would have been produced by the
cross, had not some of the nineteen flowers been on a plant which was
afterwards proved to be from some unknown cause completely sterile with
pollen of any kind. Thus far these plants behaved exactly like those in
Brazil; but later in the season, in the latter part of May and in June,
they began to produce under a net a few spontaneously self-fertilised
capsules. As soon as this occurred, sixteen flowers were fertilised with
their own pollen, and these produced five capsules, containing on an
average 3.4 seeds. At the same time I selected by chance four capsules
from the uncovered plants growing close by, the flowers of which I had
seen visited by humble-bees, and these contained on an average 21.5
seeds; so that the seeds in the naturally intercrossed capsules to those
in the self-fertilised capsules were as 100 to 16. The interesting point
in this case is that these plants, which were unnaturally treated by
being grown in pots in a hothouse, under another hemisphere, with a
complete reversal of the seasons, were thus rendered slightly
self-fertile, whereas they seem always to be completely self-sterile in
their native home.
Senecio cruentus (greenhouse varieties, commonly called Cinerarias,
probably derived from several fruticose or herbaceous species much
intercrossed (9/10. I am much obliged to Mr. Moore and to Mr. Thiselton
Dyer for giving me information with respect to the varieties on which I
experimented. Mr. Moore believes that Senecio cruentas, tussilaginis,
and perhaps heritieri, maderensis and populifolius have all been more or
less blended together in our Cinerarias.))
Public-domain text, read in full here on John Shaqi.
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