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 plants on which I experimented had been raised during two successive
generations from spontaneously self-fertilised seeds produced by plants
under a net; and as the variety is highly self-fertile, its progenitors
in Edinburgh may have been self-fertilised during some previous
generations. Several flowers on two of my plants were legitimately
crossed with pollen from a short-styled common cowslip growing almost
wild in my orchard; so that the cross was between plants which had been
subjected to considerably different conditions. Several other flowers on
the same two plants were allowed to fertilise themselves under a net;
and this union, as already explained, is a legitimate one.
The crossed and self-fertilised seeds thus obtained were sown thickly on
the opposite sides of three pots, and the seedlings thinned, so that an
equal number were left on the two sides. The seedlings during the first
year were nearly equal in height, excepting in Pot 3, Table 6/94, in
which the self-fertilised plants had a decided advantage. In the autumn
the plants were bedded out, in their pots; owing to this circumstance,
and to many plants growing in each pot, they did not flourish, and none
were very productive in seeds. But the conditions were perfectly equal
and fair for both sides. In the following spring I record in my notes
that in two of the pots the crossed plants are “incomparably the finest
in general appearance,” and in all three pots they flowered before the
self-fertilised. When in full flower the tallest flower-stem on each
side of each pot was measured, and the number of the flower-stems on
both sides counted, as shown in Table 6/94. The plants were left
uncovered, and as other plants were growing close by, the flowers no
doubt were crossed by insects. When the capsules were ripe they were
gathered and counted, and the result is likewise shown in Table 6/94.
TABLE 6/94. Primula veris (equal-styled, red-flowered variety).
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Height of tallest flower-stem: crossed Plants.
Column 3: Number of Flower-stems: crossed Plants.
Column 4: Number of good capsules: crossed Plants.
Column 5: Height of tallest flower-stem: self-fertilised Plants.
Column 6: Number of Flower-stems: self-fertilised Plants.
Column 7: Number of good capsules: self-fertilised Plants.
Pot 1 : 10 : 14 : 163 : 6 4/8 : 6 : 6.
Pot 2 : 8 4/8 : 12 : * : 5 : 2 : 0.
*Several, not counted.
Pot 3 : 7 4/8 : 7 : 43 : 10 4/8 : 5 : 26.
Totals : 26.0 : 33 : 206 : 22.0 : 13 : 32.
The average height of the three tallest flower-stems on the crossed
plants is 8.66 inches, and that of the three on the self-fertilised
plants 7.33 inches; or as 100 to 85.
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