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 fourteen crossed plants average in height 81.39 inches and the
fourteen self-fertilised plants 64.07, or as 100 to 79. One
self-fertilised plant in Pot 3 exceeded, and one in Pot 4 equalled in
height, its opponent. The self-fertilised plants showed no sign of
inheriting the precocious growth of their parents; this having been due,
as it would appear, to the abnormal state of the seeds from the
unhealthiness of their parents. The fourteen self-fertilised plants
yielded only forty spontaneously self-fertilised capsules, to which must
be added seven, the product of ten flowers artificially self-fertilised.
On the other hand, the fourteen crossed plants yielded 152 spontaneously
self-fertilised capsules; but thirty-six flowers on these plants were
crossed (yielding thirty-three capsules), and these flowers would
probably have produced about thirty spontaneously self-fertilised
capsules. Therefore an equal number of the crossed and self-fertilised
plants would have produced capsules in the proportion of about 182 to
47, or as 100 to 26. Another phenomenon was well pronounced in this
generation, but I believe had occurred previously to a slight extent;
namely, that most of the flowers on the self-fertilised plants were
somewhat monstrous. The monstrosity consisted in the corolla being
irregularly split so that it did not open properly, with one or two of
the stamens slightly foliaceous, coloured, and firmly coherent to the
corolla. I observed this monstrosity in only one flower on the crossed
plants. The self-fertilised plants, if well nourished, would almost
certainly, in a few more generations, have produced double flowers, for
they had already become in some degree sterile. (2/1. See on this
subject ‘Variation of Animals and Plants under Domestication’ chapter 18
2nd edition volume 2 page 152.)
TABLE 2/10. Ipomoea purpurea (Ninth Generation).
Heights of Plants in inches:
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 83 4/8 : 57.
Pot 1 : 85 4/8 : 71.
Pot 1 : 83 4/8 : 48 3/8.
Pot 2 : 83 2/8 : 45.
Pot 2 : 64 2/8 : 43 6/8.
Pot 2 : 64 3/8 : 38 4/8.
Pot 3 : 79 : 63.
Pot 3 : 88 1/8 : 71.
Pot 3 : 61 : 89 4/8.
Pot 4 : 82 4/8 : 82 4/8.
Pot 4 : 90 : 76 1/8.
Pot 5 : 89 4/8 : 67.
Pot 5 : 92 4/8 : 74 2/8.
Pot 5 : 92 4/8 : 70.
Crowded plants.
Total : 1139.5 : 897.0.
CROSSED AND SELF-FERTILISED PLANTS OF THE TENTH GENERATION.
Six plants were raised in the usual manner from the crossed plants of
the last generation (Table 2/10) again intercrossed, and from the
self-fertilised again self-fertilised. As one of the crossed plants in
Pot 1 in Table 2/11 became much diseased, having crumpled leaves, and
producing hardly any capsules, it and its opponent have been struck out
of the table.
TABLE 2/11. Ipomoea purpurea (Tenth Generation).
Heights of Plants in inches:
Column 1: Number (Name) of Pot.
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