The Effects of Cross & Self-Fertilisation in the Vegetable KingdomDarwin, Charles
Science
The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom
Darwin, Charles
Fertilization of plants; Plants -- Variation; Pollination
Pot 3 : 33 4/8 : 31 7/8.
Pot 3 : 29 4/8 : 28 6/8.
Pot 4 : 30 6/8 : 29 6/8.
Pot 4 : 36 : 26 3/8.
Total : 256.50 : 233.13.
The average height of the eight crossed plants is 32.06 inches, and that
of the eight self-fertilised plants 29.14; or as 100 to 90.
4. LABIATAE.--Salvia coccinea. (3/12. The admirable mechanical
adaptations in this genus for favouring or ensuring cross-fertilisation,
have been fully described by Sprengel, Hildebrand, Delpino, H. Muller,
Ogle, and others, in their several works.)
This species, unlike most of the others in the same genus, yields a good
many seeds when insects are excluded. I gathered ninety-eight capsules
produced by flowers spontaneously self-fertilised under a net, and they
contained on an average 1.45 seeds, whilst flowers artificially
fertilised with their own pollen, in which case the stigma will have
received plenty of pollen, yielded on an average 3.3 seeds, or more than
twice as many. Twenty flowers were crossed with pollen from a distinct
plant, and twenty-six were self-fertilised. There was no great
difference in the proportional number of flowers which produced capsules
by these two processes, or in the number of the contained seeds, or in
the weight of an equal number of seeds.
Seeds of both kinds were sown rather thickly on opposite sides of three
pots. When the seedlings were about 3 inches in height, the crossed
showed a slight advantage over the self-fertilised. When two-thirds
grown, the two tallest plants on each side of each pot were measured;
the crossed averaged 16.37 inches, and the self-fertilised 11.75 in
height; or as 100 to 71. When the plants were fully grown and had done
flowering, the two tallest plants on each side were again measured, with
the results shown in Table 3/27.
TABLE 3/27. Salvia coccinea.
Heights of Plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 32 6/8 : 25.
Pot 1 : 20 : 18 6/8.
Pot 2 : 32 3/8 : 20 6/8.
Pot 2 : 24 4/8 : 19 4/8.
Pot 3 : 29 4/8 : 25.
Pot 3 : 28 : 18.
Total : 167.13 : 127.00.
It may be here seen that each of the six tallest crossed plants exceeds
in height its self-fertilised opponent; the former averaged 27.85
inches, whilst the six tallest self-fertilised plants averaged 21.16
inches; or as 100 to 76. In all three pots the first plant which
flowered was a crossed one. All the crossed plants together produced 409
flowers, whilst all the self-fertilised together produced only 232
flowers; or as 100 to 57. So that the crossed plants in this respect
were far more productive than the self-fertilised.
Origanum vulgare.
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