But the self-fertilised seeds, as often occurs when few are produced, were heavier than the crossed seeds in the ratio of 100 to 90.
These two lots of seeds were sown on opposite sides of two large pots; but I succeeded in raising only four pairs of equal age. When the seedlings on both sides were about 8 inches in height they were equal. When in full flower they were measured, as follows:--
TABLE 5/74. Borago officinalis.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 19 : 13 4/8. Pot 1 : 21 : 18 6/8. Pot 1 : 16 4/8 : 20 2/8.
Pot 2 : 26 2/8 : 32 2/8.
Total : 82.75 : 84.75.
The average height of the four crossed plants is here 20.68, and that of the four self-fertilised 21.18 inches; or as 100 to 102. The self-fertilised plants thus exceeded the crossed in height by a little; but this was entirely due to the tallness of one of the self-fertilised. The crossed plants in both pots flowered before the self-fertilised. Therefore I believe if more plants had been raised, the result would have been different. I regret that I did not attend to the fertility of the two lots.
24. NOLANACEAE.--Nolana prostrata.
In some of the flowers the stamens are considerably shorter than the pistil, in others equal to it in length. I suspected, therefore, but erroneously as it proved, that this plant was dimorphic, like Primula, Linum, etc., and in the year 1862 twelve plants, covered by a net in the greenhouse, were subjected to trial. The spontaneously self-fertilised flowers yielded 64 grains weight of seeds, but the product of fourteen artificially crossed flowers is here included, which falsely increases the weight of the self-fertilised seeds. Nine uncovered plants, the flowers of which were eagerly visited by bees for their pollen and were no doubt intercrossed by them, produced 79 grains weight of seeds: therefore twelve plants thus treated would have yielded 105 grains. Thus the seeds produced by the flowers on an equal number of plants, when crossed by bees, and spontaneously self-fertilised (the product of fourteen artificially crossed flowers being, however, included in the latter) were in weight as 100 to 61.
In the summer of 1867 the trial was repeated; thirty flowers were crossed with pollen from a distinct plant and produced twenty-seven capsules, each containing five seeds. Thirty-two flowers were fertilised with their own pollen, and produced only six capsules, each with five seeds. So that the crossed and self-fertilised capsules contained the same number of seeds, though many more capsules were produced by the cross-fertilised than by the self-fertilised flowers, in the ratio of 100 to 21.
An equal number of seeds of both lots were weighed, and the crossed seeds were to the self-fertilised in weight as 100 to 82. Therefore a cross increases the number of capsules produced and the weight of the seeds, but not the number of seeds in each capsule.
These two lots of seeds, after germinating on sand, were planted on the opposite sides of three pots. The seedlings when from 6 to 7 inches in height were equal. The plants were measured when fully grown, but their heights were so unequal in the several pots, that the result cannot be fully trusted.
TABLE 5/75. Nolana prostrata.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 8 4/8 : 4 2/8. Pot 1 : 6 4/8 : 7 4/8.
Pot 2 : 10 4/8 : 14 4/8. Pot 2 : 18 : 18.
Pot 3 : 20 2/8 : 22 6/8.
Total : 63.75 : 67.00.
The five crossed plants average 12.75, and the five self-fertilised 13.4 inches in height; or as 100 to 105.
CHAPTER VI.
SOLANACEAE, PRIMULACEAE, POLYGONEAE, ETC.
Petunia violacea, crossed and self-fertilised plants compared for four generations. Effects of a cross with a fresh stock. Uniform colour of the flowers on the self-fertilised plants of the fourth generation. Nicotiana tabacum, crossed and self-fertilised plants of equal height. Great effects of a cross with a distinct sub-variety on the height, but not on the fertility, of the offspring. Cyclamen persicum, crossed seedlings greatly superior to the self-fertilised. Anagallis collina. Primula veris. Equal-styled variety of Primula veris, fertility of, greatly increased by a cross with a fresh stock. Fagopyrum esculentum. Beta vulgaris. Canna warscewiczi, crossed and self-fertilised plants of equal height. Zea mays. Phalaris canariensis.