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
The eight crossed plants were to the eight self-fertilised in height as
100 to 107. This number of plants, considering the care with which they
were raised and compared, ought to have given a trustworthy result. But
from some unknown cause they grew very unequally, and they became so
unhealthy that only three of the crossed and three of the
self-fertilised plants set any seeds, and these few in number. Under
these circumstances the mean height of neither lot can be trusted, and
the experiment is valueless. The cross-fertilised flowers on the
parent-plants yielded rather more seeds than the self-fertilised
flowers.
14. Thunbergia alata.
The six crossed plants were to the six self-fertilised in height as 100
to 108. Here the self-fertilised plants seem to have a decided
advantage; but both lots grew unequally, some of the plants in both
being more than twice as tall as others. The parent-plants also were in
an odd semi-sterile condition. Under these circumstances the superiority
of the self-fertilised plants cannot be fully trusted.
15. Nolana prostrata.
The five crossed plants were to the five self-fertilised in height as
100 to 105; so that the latter seem here to have a small but decided
advantage. On the other hand, the flowers on the parent-plants which
were cross-fertilised produced very many more capsules than the
self-fertilised flowers, in the ratio of 100 to 21; and the seeds which
the former contained were heavier than an equal number from the
self-fertilised capsules in the ratio of 100 to 82.
16. Hibiscus africanus.
Only four pairs were raised, and the crossed were to the self-fertilised
in height as 100 to 109. Excepting that too few plants were measured, I
know of nothing else to cause distrust in the result. The
cross-fertilised flowers on the parent-plants were, on the other hand,
rather more productive than the self-fertilised flowers.
17. Apium petroselinum.
A few plants (number not recorded) derived from flowers believed to have
been crossed by insects and a few self-fertilised plants were grown on
the opposite sides of four pots. They attained to a nearly equal height,
the crossed having a very slight advantage.
18. Vandellia nummularifolia.
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