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
self-fertilised seed in the same state had been planted four days
before, so that this latter seedling had a great advantage over the
crossed one. In Pot 2 the other crossed seed was planted two days before
a self-fertilised one; so that here the crossed seedling had a
considerable advantage over the self-fertilised one. But this crossed
seedling had its summit gnawed off by a slug, and was in consequence for
a time quite beaten by the self-fertilised plant. Nevertheless I allowed
it to remain, and so great was its constitutional vigour that it
ultimately beat its uninjured self-fertilised rival. When all four
plants were almost fully grown they were measured, as here shown:--
TABLE 5/54. Lathyrus odoratus.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 80 : 64 4/8.
Pot 2 : 78 4/8 : 63.
Total : 158.5 : 127.5.
The two crossed plants here average 79.25, and the two self-fertilised
63.75 inches in height, or as 100 to 80. Six flowers on these two
crossed plants were reciprocally crossed with pollen from the other
plant, and the six pods thus produced contained on an average six peas,
with a maximum in one of seven. Eighteen spontaneously self-fertilised
pods from the Painted Lady, which, as already stated, had no doubt been
self-fertilised for many previous generations, contained on an average
only 3.93 peas, with a maximum in one of five peas; so that the number
of peas in the crossed and self-fertilised pods was as 100 to 65. The
self-fertilised peas were, however, quite as heavy as those from the
crossed pods. From these two lots of seeds, the plants of the next
generation were raised.
PLANTS OF THE SECOND GENERATION.
Many of the self-fertilised peas just referred to germinated on sand
before any of the crossed ones, and were rejected. As soon as I got
equal pairs, they were planted on the opposite sides of two large pots,
which were kept in the greenhouse. The seedlings thus raised were the
grandchildren of the Painted Lady, which was first crossed by the Purple
variety. When the two lots were from 4 to 6 inches in height there was
no difference between them. Nor was there any marked difference in the
period of their flowering. When fully grown they were measured, as
follows:--
TABLE 5/55. Lathyrus odoratus (Second Generation).
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Seedlings from Plants Crossed during the two previous
Generations.
Column 3: Seedlings from Plants Self-fertilised during many previous
Generations.
Pot 1 : 72 4/8 : 57 4/8.
Pot 1 : 71 : 67.
Pot 1 : 52 2/8 : 56 2/8.
Pot 2 : 81 4/8 : 66 2/8.
Pot 2 : 45 2/8 : 38 7/8.
Pot 2 : 55 : 46.
Total : 377.50 : 331.86.
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