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
This plant, of which seeds were sent me from North Italy, produces,
besides the ordinary papilionaceous flowers, minute, imperfect, closed
or cleistogene flowers, which can never be cross-fertilised, but are
highly self-fertile. Some of the perfect flowers were crossed with
pollen from a distinct plant, and six capsules thus produced yielded on
an average 3.66 seeds, with a maximum of five in one. Twelve perfect
flowers were marked and allowed to fertilise themselves spontaneously
under a net, and they yielded eight capsules, containing on an average
2.38 seeds, with a maximum of three seeds in one. So that the crossed
and self-fertilised capsules from the perfect flowers yielded seeds in
the proportion of 100 to 65. Fifty-three capsules produced by the
cleistogene flowers contained on an average 4.1 seeds, so that these
were the most productive of all; and the seeds themselves looked finer
even than those from the crossed perfect flowers.
The seeds from the crossed perfect flowers and from the self-fertilised
cleistogene flowers were allowed to germinate on sand; but unfortunately
only two pairs germinated at the same time. These were planted on the
opposite sides of the same pot, which was kept in the greenhouse. In the
summer of the same year, when the seedlings were about 4 1/2 inches in
height, the two lots were equal. In the autumn of the following year
(1868) the two crossed plants were of exactly the same height, namely,
11 4/8 inches, and the two self-fertilised plants 12 6/8 and 7 2/8
inches; so that one of the self-fertilised exceeded considerably in
height all the others. By the autumn of 1869 the two crossed plants had
acquired the supremacy; their height being 16 4/8 and 15 1/8, whilst
that of the two self-fertilised plants was 14 5/8 and 11 4/8 inches.
By the autumn of 1870, the heights were as follows:--
TABLE 5/61. Ononis minutissima.
Heights of plants measured in inches.
Column 1: Crossed Plants.
Column 2: Self-fertilised Plants.
: 20 3/8 : 17 4/8.
: 19 2/8 : 17 2/8.
Total : 39.63 : 34.75.
So that the mean height of the two crossed plants was 19.81, and that of
the two self-fertilised 17.37 inches; or as 100 to 88. It should be
remembered that the two lots were at first equal in height; that one of
the self-fertilised plants then had the advantage, the two crossed
plants being at last victorious.]
SUMMARY ON THE LEGUMINOSAE.
Public-domain text, read in full here on John Shaqi.
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