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.
Ipomoea purpurea--seeds per capsule on crossed and self-fertilised plants from the same parents as in the last case, but growing much crowded, spontaneously self-fertilised under a net, in number: 93.
Ipomoea purpurea--productiveness of the same plants, as judged by the number of capsules produced, and average number of seeds per capsule: 45.
Ipomoea purpurea--third generation: seeds per capsule on crossed and self-fertilised plants, spontaneously self-fertilised under a net, in number: 94.
Ipomoea purpurea--productiveness of the same plants, as judged by the number of capsules produced, and the average number of seeds per capsule: 35.
Ipomoea purpurea--fifth generation: seeds per capsule on crossed and self-fertilised plants, left uncovered in the hothouse, and spontaneously fertilised: 89.
Ipomoea purpurea--ninth generation: number of capsules on crossed plants to those on self-fertilised plants, spontaneously self-fertilised under a net: 26.
Mimulus luteus--an equal number of capsules on plants descended from self-fertilised plants of the 8th generation crossed by a fresh stock, and on plants of the 9th self-fertilised generation, both sets having been left uncovered and spontaneously fertilised, contained seeds, by weight: 30.
Mimulus luteus--productiveness of the same plants, as judged by the number of capsules produced, and the average weight of seeds per capsule: 3.
Vandellia nummularifolia--seeds per capsule from cleistogene flowers on the crossed and self-fertilised plants, in number: 106.
Salvia coccinea--crossed plants, compared with self-fertilised plants, produced flowers, in number: 57.
Iberis umbellata--plants left uncovered in greenhouse; intercrossed plants of the 3rd generation, compared with self-fertilised plants of the 3rd generation, yielded seeds, in number: 75.
Iberis umbellata--plants from a cross between two varieties, compared with self-fertilised plants of the 3rd generation, yielded seeds, by weight : 75.
Papaver vagum--crossed and self-fertilised plants, left uncovered, produced capsules, in number: 99.
Eschscholtzia californica--Brazilian stock; plants left uncovered and cross-fertilised by bees; capsules on intercrossed plants of the 2nd generation, compared with capsules on self-fertilised plants of 2nd generation, contained seeds, in number: 78.
Eschscholtzia californica--productiveness of the same plants, as judged by the number of capsules produced, and the average number of seeds per capsule: 89.
Eschscholtzia californica--plants left uncovered and cross-fertilised by bees; capsules on plants derived from intercrossed plants of the 2nd generation of the Brazilian stock crossed by English stock, compared with capsules on self-fertilised plants of 2nd generation, contained seeds, in number: 63.