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
Twelve flowers on some plants in my flower-garden were fertilised with
pollen from distinct plants, and produced twelve capsules; but one of
these contained no good seed. The seeds of the eleven good capsules
weighed 17.4 grains. Eighteen flowers on the same plants were fertilised
with their own pollen and produced twelve good capsules, which contained
13.61 grains weight of seed. Therefore an equal number of crossed and
self-fertilised capsules would have yielded seed by weight as 100 to 71.
(4/4. Professor Hildebrand experimented on plants in Germany on a larger
scale than I did, and found them much more self-fertile. Eighteen
capsules, produced by cross-fertilisation, contained on an average
eighty-five seeds, whilst fourteen capsules from self-fertilised flowers
contained on an average only nine seeds; that is, as 100 to 11: ‘Jahrb.
fur Wissen Botanik.’ B. 7 page 467.) If we take into account of the fact
that a much greater proportion of flowers produced capsules when crossed
than when self-fertilised, the relative fertility of the crossed to the
self-fertilised flowers was as 100 to 52. Nevertheless these plants,
whilst still protected by the net, spontaneously produced a considerable
number of self-fertilised capsules.
The seeds of the two lots after germinating on sand were planted in
pairs on the opposite sides of four large pots. At first there was no
difference in their growth, but ultimately the crossed seedlings
exceeded the self-fertilised considerably in height, as shown in Table
4/34. But I believe from the cases which follow that this result was
accidental, owing to only a few plants having been measured, and to one
of the self-fertilised plants having grown only to a height of 15
inches. The plants had been kept in the greenhouse, and from being drawn
up to the light had to be tied to sticks in this and the following
trials. They were measured to the summits of their flower-stems.
TABLE 4/34. Eschscholtzia californica.
Heights of Plants to the summits of their flower-stems measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 33 4/8 : 25.
Pot 2 : 34 2/8 : 35.
Pot 3 : 29 : 27 2/8.
Pot 4 : 22 : 15.
Total : 118.75 : 102.25.
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