I did not at the time think of this source of error, but I now suspect that the growth of the crossed plants was thus injured. Anyhow the trial was not perfectly fair. Opposed to the belief that the pollen used in crossing was not in so good a state as that used for self-fertilisation, is the fact that a greater proportional number of the crossed than of the self-fertilised flowers produced capsules; but there was no marked difference in the amount of seed contained in the capsules of the two lots. (5/24. Gartner has shown that certain plants of Lobelia fulgens are quite sterile with pollen from the same plant, though this pollen is efficient on any other individual; but none of the plants on which I experimented, which were kept in the greenhouse, were in this peculiar condition.)
As the seeds obtained by the above two methods would not germinate when left on bare sand, they were sown on the opposite sides of four pots; but I succeeded in raising only a single pair of seedlings of the same age in each pot. The self-fertilised seedlings, when only a few inches in height, were in most of the pots taller than their opponents; and they flowered so much earlier in all the pots, that the height of the flower-stems could be fairly compared only in Pots 1 and 2.
TABLE 5/70. Lobelia fulgens (First Generation).
Heights of flower-stems measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Height of Flower-stems on the Crossed Plants.
Column 3: Height of Flower-stems on the Self-fertilised Plants.
Pot 1 : 33 : 50.
Pot 2 : 36 4/8 : 38 4/8.
Pot 3 : 21* : 43.
Pot 4 : 12* : 35 6/8.
*Not in full flower.
The mean height of the flower-stems of the two crossed plants in Pots 1 and 2 is here 34.75 inches, and that of the two self-fertilised plants in the same pots 44.25 inches; or as 100 to 127. The self-fertilised plants in Pots 3 and 4 were in every respect very much finer than the crossed plants.
I was so much surprised at this great superiority of the self-fertilised over the crossed plants, that I determined to try how they would behave in one of the pots during a second growth. The two plants, therefore, in Pot 1 were cut down, and repotted without being disturbed in a much larger pot. In the following year the self-fertilised plant showed even a greater superiority than before; for the two tallest flower-stems produced by the one crossed plant were only 29 4/8 and 30 1/8 inches in height, whereas the two tallest stems on the one self-fertilised plant were 49 4/8 and 49 6/8 inches; and this gives a ratio of 100 to 167. Considering all the evidence, there can be no doubt that these self-fertilised plants had a great superiority over the crossed plants.
CROSSED AND SELF-FERTILISED PLANTS OF THE SECOND GENERATION.
TABLE 5/71. Lobelia fulgens (Second Generation).
Heights of flower-stems measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 27 3/8 : 32 3/8. Pot 1 : 26 : 26 3/8. Pot 1 : 24 3/8 : 25 1/8. Pot 1 : 24 4/8 : 26 2/8.
Pot 2 : 34 : 36 2/8. Pot 2 : 26 6/8 : 28 6/8. Pot 2 : 25 1/8 : 30 1/8. Pot 2 : 26 : 32 2/8.
Pot 3 : 40 4/8 : 30 4/8. Pot 3 : 37 5/8 : 28 2/8. Pot 3 : 32 1/8 : 23.
Pot 4 : 34 5/8 : 29 4/8. Pot 4 : 32 2/8 : 28 3/8. Pot 4 : 29 3/8 : 26. Pot 4 : 27 1/8 : 25 2/8.
Pot 5 : 28 1/8 : 29. Pot 5 : 27 : 24 6/8. Pot 5 : 25 3/8 : 23 2/8. Pot 5 : 24 3/8 : 24.
Pot 6 : 33 5/8 : 44 2/8. Pot 6 : 32 : 37 6/8. Pot 6 : 26 1/8 : 37. Pot 6 : 25 : 35.
Pot 7 : 30 6/8 : 27 2/8. Pot 7 : 30 3/8 : 19 2/8. Pot 7 : 29 2/8 : 21.
Pot 8 : 39 3/8 : 23 1/8. Pot 8 : 37 2/8 : 23 4/8. Pot 8 : 36 : 25 4/8. Pot 8 : 36 : 25 1/8.
Pot 9 : 33 3/8 : 19 3/8. Pot 9 : 25 : 16 3/8. Pot 9 : 25 3/8 : 19. Pot 9 : 21 7/8 : 18 6/8.
Total : 1014.00 : 921.63.
I determined on this occasion to avoid the error of using pollen of not quite equal maturity for crossing and self-fertilisation; so that I squeezed pollen out of the conjoined anthers of young flowers for both operations.