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
Pot 6 : 28 2/8 : 18 6/8 : 12.
Pot 6 : 22 : 7 : 16 1/8.
Pot 6 : -- : 12 4/8 : --.
Pot 7 : 12 4/8 : 15 : --.
Pot 7 : 24 3/8 : 12 3/8 : --.
Pot 7 : 20 4/8 : 11 2/8 : --.
Pot 7 : 26 4/8 : 15 2/8 : --.
Pot 8 : 17 2/8 : 13 3/8 : --.
Pot 8 : 22 6/8 : 14 5/8 : --.
Pot 8 : 27 : 14 3/8 : --.
Pot 9 : 22 6/8 : 11 6/8 : --.
Pot 9 : 6 : 17 : --.
Pot 9 : 20 2/8 : 14 7/8 : --.
Pot 10 : 18 1/8 : 9 2/8 : 10 3/8.
Pot 10 : 16 5/8 : 8 2/8 : 8 1/8.
Pot 10 : 17 4/8 : 10 : 11 2/8.
Crowded plants.
Total : 605.38 : 329.50 : 198.50.
In this table the average height of the twenty-eight Chelsea-crossed
plants is 21.62 inches; that of the twenty-seven intercrossed plants
12.2; and that of the nineteen self-fertilised 10.44. But with respect
to the latter it will be the fairest plan to strike out two dwarfed ones
(only 4 inches in height), so as not to exaggerate the inferiority of
the self-fertilised plants; and this will raise the average height of
the seventeen remaining self-fertilised plants to 11.2 inches. Therefore
the Chelsea-crossed are to the intercrossed in height as 100 to 56; the
Chelsea-crossed to the self-fertilised as 100 to 52; and the
intercrossed to the self-fertilised as 100 to 92. We thus see how
immensely superior in height the Chelsea-crossed are to the intercrossed
and to the self-fertilised plants. They began to show their superiority
when only one inch high. They were also, when fully grown, much more
branched with larger leaves and somewhat larger flowers than the plants
of the other two lots, so that if they had been weighed, the ratio would
certainly have been much higher than that of 100 to 56 and 52.
The intercrossed plants are here to the self-fertilised in height as 100
to 92; whereas in the analogous experiment given in Table 3/19 the
intercrossed plants from the self-fertilised plants of the sixth
generation were inferior in height to the self-fertilised plants in the
ratio of 100 to 110. I doubt whether this discordance in the results of
the two experiments can be explained by the self-fertilised plants in
the present case having been raised from spontaneously self-fertilised
seeds, whereas in the former case they were raised from artificially
self-fertilised seeds; nor by the present plants having been
self-fertilised during two additional generations, though this is a more
probable explanation.
With respect to fertility, the twenty-eight Chelsea-crossed plants
produced 272 capsules; the twenty-seven intercrossed plants produced 24;
and the seventeen self-fertilised plants 17 capsules. All the plants
were left uncovered so as to be naturally fertilised, and empty capsules
were rejected.
Therefore 20 Chelsea-crossed plants would have produced 194.29 capsules.
Therefore 20 Intercrossed plants would have produced 17.77 capsules.
Therefore 20 Self-fertilised plants would have produced 20.00 capsules.
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