Owing to the varieties having been self-fertilised for many generations,
and to their having been subjected in each generation to nearly the same
conditions (as will be explained in a future chapter) I did not expect
that a cross between two such plants would benefit the offspring; and so
it proved on trial. In 1867 I covered up several plants of the Early
Emperor pea, which was not then a very new variety, so that it must
already have been propagated by self-fertilisation for at least a dozen
generations. Some flowers were crossed with pollen from a distinct plant
growing in the same row, and others were allowed to fertilise themselves
under a net. The two lots of seeds thus obtained were sown on opposite
sides of two large pots, but only four pairs came up at the same time.
The pots were kept in the greenhouse. The seedlings of both lots when
between 6 and 7 inches in height were equal. When nearly full-grown they
were measured, as in Table 5/57.
TABLE 5/57. Pisum sativum.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 35 : 29 6/8.
Pot 2 : 31 4/8 : 51.
Pot 2 : 35 : 45.
Pot 2 : 37 : 33.
Total : 138.50 : 158.75.
The average height of the four crossed plants is here 34.62, and that of
the four self-fertilised plants 39.68, or as 100 to 115.
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