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Darwin, Charles, 1809-1882

"Effects of Cross and Self Fertilisation in the Vegetable Kingdom"

The result was
surprising, for the self-fertilised seedlings very early in life beat
the crossed, and at one time were nearly double their height. At first
the case appeared like that of Mimulus, in which after the third
generation a tall and highly self-fertile variety appeared. But as in
the two succeeding generations the crossed plants resumed their former
superiority over the self-fertilised, the case must be looked at as an
anomaly. The sole conjecture which I can form is that the crossed seeds
had not been sufficiently ripened, and thus produced weakly plants, as
occurred with Iberis. When the crossed plants were between 3 and 4
inches in height, the six finest in four of the pots were measured to
the summits of their stems, and at the same time the six finest of the
self-fertilised plants. The measurements are given in Table 6/78, and it
may be here seen that all the self-fertilised plants exceed their
opponents in height, whereas when subsequently measured the excess of
the self-fertilised depended chiefly on the unusual tallness of two of
the plants in Pot 2. The crossed plants here average 3.27, and the
self-fertilised 6.08 inches in height; or as 100 to 186.
When fully grown they were again measured, as follows:--
TABLE 6/79. Petunia violacea (third generation; plants fully grown).
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.


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