But from various causes,
chiefly from the want of time, I was often compelled to rely on the
number of the capsules alone. Nevertheless, in the more interesting
cases, the seeds were also counted or weighed. The average number of
seeds per capsule is a more valuable criterion of fertility than the
number of capsules produced. This latter circumstance depends partly on
the size of the plant; and we know that crossed plants are generally
taller and heavier than the self-fertilised; but the difference in this
respect is rarely sufficient to account for the difference in the number
of the capsules produced. It need hardly be added that in Table 9/D the
same number of crossed and self-fertilised plants are always compared.
Subject to the foregoing sources of doubt I will now give the table, in
which the parentage of the plants experimented on, and the manner of
determining their fertility are explained. Fuller details may be found
in the previous part of this work, under the head of each species.
TABLE 9/D.--RELATIVE FERTILITY OF PLANTS OF CROSSED AND SELF-FERTILISED
PARENTAGE, BOTH SETS BEING FERTILISED IN THE SAME MANNER. FERTILITY
JUDGED OF BY VARIOUS STANDARDS. THAT OF THE CROSSED PLANTS TAKEN AS 100.
Column 1: Name of plant and feature observed.
Column 2: x, in the expression, as 100 to x.
Ipomoea purpurea--first generation: seeds per capsule on crossed and
self-fertilised plants, not growing much crowded, spontaneously
self-fertilised under a net, in number: 99.
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