artificially cross-fertilised capsules) seventy-seven self-fertilised
capsules containing on an average 4.41 seeds; whilst the three
self-fertilised plants produced spontaneously (besides the twenty-three
artificially self-fertilised capsules) only twenty-nine self-fertilised
capsules, containing on an average 4.14 seeds. Therefore the average
number of seeds in the two lots of spontaneously self-fertilised
capsules was as 100 to 94. Taking into consideration the number of
capsules together with the average number of seeds, the crossed plants
(spontaneously self-fertilised) produced seeds in comparison with the
self-fertilised plants (spontaneously self-fertilised) in the proportion
of 100 to 35. By whatever method the fertility of these plants is
compared, the crossed are more fertile than the self-fertilised plants.

I tried in several ways the comparative vigour and powers of growth of
the crossed and self-fertilised plants of this third generation. Thus,
four self-fertilised seeds which had just germinated were planted on one
side of a pot, and after an interval of forty-eight hours, four crossed
seeds in the same state of germination were planted on the opposite
side; and the pot was kept in the hothouse. I thought that the advantage
thus given to the self-fertilised seedlings would have been so great
that they would never have been beaten by the crossed ones. They were
not beaten until all had grown to a height of 18 inches; and the degree
to which they were finally beaten is shown in Table 2/4. We here see
that the average height of the four crossed plants is 76.62, and of the
four self-fertilised plants 65.87 inches, or as 100 to 86; therefore
less than when both sides started fair.

TABLE 2/4. Ipomoea purpurea (Third Generation, the self-fertilised
plants having had a start of forty-eight hours).