The plants in Pots 1
and 2 were measured when between 7 and 8 inches in height, and the
crossed exceeded the self-fertilised in average height by 1.57 inches.
When fully grown they were again measured to the summits of their
flower-heads, with the following result:--
TABLE 4/31. Iberis umbellata.
Heights of plants to the summits of their flower-heads, in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants of the Third Generation.
Pot 1 : 18 : 19.
Pot 1 : 21 : 21.
Pot 1 : 18 2/8 : 19 4/8.
Pot 2 : 19 : 16 6/8.
Pot 2 : 18 4/8 : 7 4/8.
Pot 2 : 17 6/8 : 14 4/8.
Pot 2 : 21 3/8 : 16 4/8.
Total : 133.88 : 114.75.
The average height of the seven crossed plants is here 19.12 inches, and
that of the seven self-fertilised plants 16.39, or as 100 to 86. But as
the plants on the self-fertilised side grew very unequally, this ratio
cannot be fully trusted, and is probably too high. In both pots a
crossed plant flowered before any one of the self-fertilised. These
plants were left uncovered in the greenhouse; but from being too much
crowded they were not very productive. The seeds from all seven plants
of both lots were counted; the crossed produced 206, and the
self-fertilised 154; or as 100 to 75.
CROSS BY A FRESH STOCK.
From the doubts caused by the two first trials, in which it was not
known with certainty that the plants had been crossed; and from the
crossed plants in the last experiment having been put into competition
with plants self-fertilised for three generations, which moreover grew
very unequally, I resolved to repeat the trial on a larger scale, and in
a rather different manner.
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