But in the present instance the seeds from the crossed capsules were separated into two lots,--namely, those from the capsules containing over fourteen seeds, and those from the capsules containing under fourteen seeds, and the seeds from the more productive capsules were the heavier of the two; so that the above explanation here fails.
As pollen is deposited at a very early age on the pistil, generally in contact with the stigma, some flowers whilst still in bud were castrated for my first experiment, and were afterwards fertilised with pollen from a distinct plant. Other flowers were fertilised with their own pollen. From the seeds thus obtained, I succeeded in rearing only three pairs of plants of equal age. The three crossed plants averaged 32.79 inches, and the three self-fertilised 32.08 inches in height; so that they were nearly equal, the crossed having a slight advantage. As the same result followed in all three generations, it would be superfluous to give the heights of all the plants, and I will give only the averages.
In order to raise crossed and self-fertilised plants of the second generation, some flowers on the above crossed plants were crossed within twenty-four hours after they had expanded with pollen from a distinct plant; and this interval would probably not be too great to allow of cross-fertilisation being effectual. Some flowers on the self-fertilised plants of the last generation were also self-fertilised. From these two lots of seeds, ten crossed and twelve self-fertilised plants of equal ages were raised; and these were measured when fully grown. The crossed averaged 36.98, and the self-fertilised averaged 37.42 inches in height; so that here again the two lots were nearly equal; but the self-fertilised had a slight advantage.
In order to raise plants of the third generation, a better plan was followed, and flowers on the crossed plants of the second generation were selected in which the stamens were too short to reach the stigmas, so that they could not possibly have been self-fertilised. These flowers were crossed with pollen from a distinct plant. Flowers on the self-fertilised plants of the second generation were again self-fertilised. From the two lots of seeds thus obtained, twenty-one crossed and nineteen self-fertilised plants of equal age, and forming the third generation, were raised in fourteen large pots. They were measured when fully grown, and by an odd chance the average height of the two lots was exactly the same, namely, 35.96 inches; so that neither side had the least advantage over the other. To test this result, all the plants on both sides in ten out of the above fourteen pots were cut down after they had flowered, and in the ensuing year the stems were again measured; and now the crossed plants exceeded by a little (namely, 1.7 inches) the self-fertilised. They were again cut down, and on their flowering for the third time, the self-fertilised plants had a slight advantage (namely, 1.54 inches) over the crossed. Hence the result arrived at with these plants during the previous trials was confirmed, namely, that neither lot had any decided advantage over the other. It may, however, be worth mentioning that the self-fertilised plants showed some tendency to flower before the crossed plants: this occurred with all three pairs of the first generation; and with the cut down plants of the third generation, a self-fertilised plant flowered first in nine out of the twelve pots, whilst in the remaining three pots a crossed plant flowered first.
If we consider all the plants of the three generations taken together, the thirty-four crossed plants average 35.98, and the thirty-four self-fertilised plants 36.39 inches in height; or as 100 to 101. We may therefore conclude that the two lots possessed equal powers of growth; and this I believe to be the result of long-continued self-fertilisation, together with exposure to similar conditions in each generation, so that all the individuals had acquired a closely similar constitution.