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 Westerham-crossed plants in weight to the intercrossed as 100 to
101.
The intercrossed plants in weight to the self-fertilised as 100 to 22.3.
We here see, judging by weight instead of as before by height, that the
Westerham-crossed and the intercrossed have an immense advantage over
the self-fertilised. The Westerham-crossed are inferior to the
intercrossed by a mere trifle; but it is almost certain that if they had
been allowed to go on growing for another month, the former would have
completely beaten the latter.
As I had an abundance of seeds of the same three lots, from which the
foregoing plants had been raised, these were sown in three long parallel
and adjoining rows in the open ground, so as to ascertain whether under
these circumstances the results would be nearly the same as before. Late
in the autumn (November 13) the ten tallest plants were carefully
selected out of each row, and their heights measured, with the following
result:--
TABLE 6/83. Petunia violacea (plants growing in the open ground).
Heights of plants measured in inches.
Column 1: Westerham-Crossed Plants (from self-fertilised Plants of the
fourth generation crossed by a fresh stock).
Column 2: intercrossed Plants (Plants of one and the same stock
intercrossed for five generations).
Column 3: self-fertilised Plants (self-fertilised for five generations).
34 2/8 : 38 : 27 3/8.
36 2/8 : 36 2/8 : 23.
35 2/8 : 39 5/8 : 25.
32 4/8 : 37 : 24 1/8.
37 : 36 : 22 4/8.
36 4/8 : 41 3/8 : 23 3/8.
40 7/8 : 37 2/8 : 21 5/8.
37 2/8 : 40 : 23 4/8.
38 2/8 : 41 2/8 : 21 3/8.
38 5/8 : 36 : 21 2/8.
366.76 : 382.76 : 233.13.
The ten Westerham-crossed plants here average 36.67 inches in height;
the ten intercrossed plants, 38.27 inches; and the ten self-fertilised,
23.31 inches. These three lots of plants were also weighed; the
Westerham-crossed plants weighed 28 ounces; the intercrossed plants, 41
ounces; and the self-fertilised, 14.75 ounces. We thus get the following
ratios:--
The Westerham-crossed plants in height to the self-fertilised as 100 to
63.
The Westerham-crossed plants in weight to the self-fertilised as 100 to
53.
The Westerham-crossed plants in height to the intercrossed as 100 to
104.
The Westerham-crossed plants in weight to the intercrossed as 100 to
146.
The intercrossed plants in height to the self-fertilised as 100 to 61.
The intercrossed plants in weight to the self-fertilised as 100 to 36.
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