Column 1: Number (Name) of Pot.
Column 2: Crossed Plants (two tallest in each pot).
Column 3: Self-fertilised Plants (two tallest in each pot).
Pot 1 : 26 : 24. Pot 1 : 21 : 21.
Pot 2 : 17 : 12. Pot 2 : 16 : 11 4/8.
Total : 80.0 : 68.5.
The average height of the crossed plants is here 20 inches, and that of the self-fertilised 17.12; or as 100 to 86. But this excess of height by no means gives a fair idea of the vast superiority in vigour of the crossed over the self-fertilised plants. The crossed flowered first and produced thirty flower-stems, whilst the self-fertilised produced only fifteen, or half the number. The pots were then bedded out, and the roots probably came out of the holes at the bottom and thus aided their growth. Early in the following summer the superiority of the crossed plants, owing to their increase by stolons, over the self-fertilised plants was truly wonderful. In Pot 1, and it should be remembered that very large pots had been used, the oval clump of crossed plants was 10 by 4 1/2 inches across, with the tallest stem, as yet young, 5 1/2 inches in height; whilst the clump of self-fertilised plants, on the opposite side of the same pot, was only 3 1/2 by 2 1/2 inches across, with the tallest young stem 4 inches in height. In Pot 2, the clump of crossed plants was 18 by 9 inches across, with the tallest young stem 8 1/2 inches in height; whilst the clump of self-fertilised plants on the opposite side of the same pot was 12 by 4 1/2 inches across, with the tallest young stem 6 inches in height. The crossed plants during this season, as during the last, flowered first. Both the crossed and self-fertilised plants being left freely exposed to the visits of bees, manifestly produced much more seed than their grand-parents,—the plants of the original clump still growing close by in the same garden, and equally left to the action of the bees.
5. ACANTHACEAE.—Thunbergia alata.
It appears from Hildebrand’s description (‘Botanische Zeitung’ 1867 page 285) that the conspicuous flowers of this plant are adapted for cross-fertilisation. Seedlings were twice raised from purchased seed; but during the early summer, when first experimented on, they were extremely sterile, many of the anthers containing hardly any pollen. Nevertheless, during the autumn these same plants spontaneously produced a good many seeds. Twenty-six flowers during the two years were crossed with pollen from a distinct plant, but they yielded only eleven capsules; and these contained very few seeds! Twenty-eight flowers were fertilised with pollen from the same flower, and these yielded only ten capsules, which, however, contained rather more seed than the crossed capsules. Eight pairs of germinating seeds were planted on opposite sides of five pots; and exactly half the crossed and half the self-fertilised plants exceeded their opponents in height. Two of the self-fertilised plants died young, before they were measured, and their crossed opponents were thrown away. The six remaining pairs of these grew very unequally, some, both of the crossed and self-fertilised plants, being more than twice as tall as the others. The average height of the crossed plants was 60 inches, and that of the self-fertilised plants 65 inches, or as 100 to 108. A cross, therefore, between distinct individuals here appears to do no good; but this result deduced from so few plants in a very sterile condition and growing very unequally, obviously cannot be trusted.]