Other flowers on the same plants of the eighth self-fertilised generation were crossed with pollen taken from another plant of the same lot; so that the seedlings thus raised were the offspring of eight previous generations of self-fertilisation with an intercross in the last generation; these I will call the INTERCROSSED PLANTS. Lastly, other flowers on the same plants of the eighth self-fertilised generation were crossed with pollen taken from plants which had been raised from seed procured from a garden at Chelsea. The Chelsea plants bore yellow flowers blotched with red, but differed in no other respect. They had been grown out of doors, whilst mine had been cultivated in pots in the greenhouse for the last eight generations, and in a different kind of soil. The seedlings raised from this cross with a wholly different stock may be called the CHELSEA-CROSSED. The three lots of seeds thus obtained were allowed to germinate on bare sand; and whenever a seed in all three lots, or in only two, germinated at the same time, they were planted in pots superficially divided into three or two compartments. The remaining seeds, whether or not in a state of germination, were thickly sown in three divisions in a large pot, 10, in Table 3/20. When the plants had grown to their full height they were measured, as shown in Table 3/20; but only the three tallest plants in each of the three divisions in Pot 10 were measured.

TABLE 3/20. Mimulus luteus.

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Plants from Self-fertilised Plants of the Eighth Generation crossed by Chelsea Plants.

Column 3: Plants from an intercross between the Plants of the Eighth Self-fertilised Generation.

Column 4: Self-fertilised Plants of the Ninth Generation from Plants of the Eighth Self-fertilised Generation.

Pot 1 : 30 7/8 : 14 : 9 4/8. Pot 1 : 28 3/8 : 13 6/8 : 10 5/8. Pot 1 : -- : 13 7/8 : 10.

Pot 2 : 20 6/8 : 11 4/8 : 11 6/8. Pot 2 : 22 2/8 : 12 : 12 3/8. Pot 2 : -- : 9 1/8 : --.

Pot 3 : 23 6/8 : 12 2/8 : 8 5/8. Pot 3 : 24 1/8 : -- : 11 4/8. Pot 3 : 25 6/8 : -- : 6 7/8.

Pot 4 : 22 5/8 : 9 2/8 : 4. Pot 4 : 22 : 8 1/8 : 13 3/8. Pot 4 : 17 : -- : 11.

Pot 5 : 22 3/8 : 9 : 4 4/8. Pot 5 : 19 5/8 : 11 : 13. Pot 5 : 23 4/8 : -- : 13 4/8.

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 Effects of Cross and Self-Fertilisation in the Vegetable Kingdom Page 37

19th Century English Literature

Charles Darwin

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Charles Darwin

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