When fully grown the same plants were again measured, with the result shown in Table 3/18.

TABLE 3/18. Mimulus luteus (Seventh Generation).

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Crossed Plants.

Column 3: Self-fertilised Plants.

Pot 1 : 11 2/8 : 19 1/8. Pot 1 : 11 7/8 : 18.

Pot 2 : 12 6/8 : 18 2/8. Pot 2 : 11 2/8 : 14 6/8.

Pot 3 : 9 6/8 : 12 6/8. Pot 3 : 11 6/8 : 11.

Total : 68.63 : 93.88.

The average height of the six crossed is here 11.43, and that of the six self-fertilised 15.64, or as 100 to 137.

As it is now evident that the tall white variety transmitted its characters faithfully, and as the self-fertilised plants consisted exclusively of this variety, it was manifest that they would always exceed in height the crossed plants which belonged chiefly to the original shorter varieties. This line of experiment was therefore discontinued, and I tried whether intercrossing two self-fertilised plants of the sixth generation, growing in distinct pots, would give their offspring any advantage over the offspring of flowers on one of the same plants fertilised with their own pollen. These latter seedlings formed the seventh generation of self-fertilised plants, like those in the right hand column in Table 3/18; the crossed plants were the product of six previous self-fertilised generations with an intercross in the last generation. The seeds were allowed to germinate on sand, and were planted in pairs on opposite sides of four pots, all the remaining seeds being sown crowded on opposite sides of Pot 5 in Table 3/19; the three tallest on each side in this latter pot being alone measured. All the plants were twice measured--the first time whilst young, and the average height of the crossed plants to that of the self-fertilised was then as 100 to 122. When fully grown they were again measured, as in Table 3/19.

TABLE 3/19. Mimulus luteus.

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Intercrossed Plants from Self-fertilised Plants of the Sixth Generation.

Column 3: Self-fertilised Plants of the Seventh Generation.

Pot 1 : 12 6/8 : 15 2/8. Pot 1 : 10 4/8 : 11 5/8. Pot 1 : 10 : 11. Pot 1 : 14 5/8 : 11.

Pot 2 : 10 2/8 : 11 3/8. Pot 2 : 7 6/8 : 11 4/8. Pot 2 : 12 1/8 : 8 5/8. Pot 2 : 7 : 14 3/8.

Pot 3 : 13 5/8 : 10 3/8. Pot 3 : 12 2/8 : 11 6/8.

Pot 4 : 7 1/8 : 14 6/8. Pot 4 : 8 2/8 : 7. Pot 4 : 7 2/8 : 8.

Pot 5 : 8 5/8 : 10 2/8 Pot 5 : 9 : 9 3/8. Pot 5 : 8 2/8 : 9 2/8. Crowded.

Total : 159.38 : 175.50.

The average height of the sixteen intercrossed plants is here 9.96 inches, and that of the sixteen self-fertilised plants 10.96, or as 100 to 110; so that the intercrossed plants, the progenitors of which had been self-fertilised for the six previous generations, and had been exposed during the whole time to remarkably uniform conditions, were somewhat inferior in height to the plants of the seventh self-fertilised generation. But as we shall presently see that a similar experiment made after two additional generations of self-fertilisation gave a different result, I know not how far to trust the present one. In three of the five pots in Table 3/19 a self-fertilised plant flowered first, and in the other two a crossed plant. These self-fertilised plants were remarkably fertile, for twenty flowers fertilised with their own pollen produced no less than nineteen very fine capsules!

THE EFFECTS OF A CROSS WITH A DISTINCT STOCK.

Some flowers on the self-fertilised plants in Pot 4 in Table 3/19 were fertilised with their own pollen, and plants of the eighth self-fertilised generation were thus raised, merely to serve as parents in the following experiment. Several flowers on these plants were allowed to fertilise themselves spontaneously (insects being of course excluded), and the plants raised from these seeds formed the ninth self-fertilised generation; they consisted wholly of the tall white variety with crimson blotches.

The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom Page 36

19th Century English Literature

Charles Darwin

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Charles Darwin

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