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
Some flowers on a crossed plant of the last or second generation were
fertilised, without being castrated, by pollen taken from a plant of the
same variety, but not related to my plants, and brought from a nursery
garden (whence my seeds originally came) having a different soil and
aspect. The flowers on the self-fertilised plants of the last or second
generation (Table 4/29) were allowed to fertilise themselves
spontaneously under a net, and yielded plenty of seeds. These latter and
the crossed seeds, after germinating on sand, were planted in pairs on
the opposite sides of six large pots, which were kept at first in a cool
greenhouse. Early in January their heights were measured to the tips of
their leaves. The thirteen crossed plants averaged 13.16 inches in
height, and the twelve (for one had died) self-fertilised plants
averaged 13.7 inches, or as 100 to 104; so that the self-fertilised
plants exceeded by a little the crossed plants.
TABLE 3/30. Brassica oleracea.
Weights in ounces of plants after they had formed heads.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants from Pollen of fresh Stock.
Column 3: Self-fertilised Plants of the Third Generation.
Pot 1 : 130 : 18 2/4.
Pot 2 : 74 : 34 3/4.
Pot 3 : 121 : 17 2/4.
Pot 4 : 127 2/4 : 14.
Pot 5 : 90 : 11 2/4.
Pot 6 : 106 2/4 : 46.
Total : 649.00 : 142.25.
Early in the spring the plants were gradually hardened, and turned out
of their pots into the open ground without being disturbed. By the end
of August the greater number had formed fine heads, but several grew
extremely crooked, from having been drawn up to the light whilst in the
greenhouse. As it was scarcely possible to measure their heights, the
finest plant on each side of each pot was cut down close to the ground
and weighed. In Table 4/30 we have the result.
The six finest crossed plants average 108.16 ounces, whilst the six
finest self-fertilised plants average only 23.7 ounces, or as 100 to 22.
This difference shows in the clearest manner the enormous benefit which
these plants derived from a cross with another plant belonging to the
same sub-variety, but to a fresh stock, and grown during at least the
three previous generations under somewhat different conditions.
THE OFFSPRING FROM A CUT-LEAVED, CURLED, AND VARIEGATED WHITE-GREEN
CABBAGE CROSSED WITH A CUT-LEAVED, CURLED, AND VARIEGATED CRIMSON-GREEN
CABBAGE, COMPARED WITH THE SELF-FERTILISED OFFSPRING FROM THE TWO
VARIETIES.
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