We have seen in Table 7/C that the whole advantage of
a cross by a fresh stock is confined to fertility, and so it was with
the intercrossed plants of the same stock compared with the
self-fertilised, for the former were in fertility to the latter as 100
to 89. The intercrossed plants thus have at least one important
advantage over the self-fertilised. Moreover, the flowers on the
parent-plants when fertilised with pollen from another individual of the
same stock yield far more seeds than when self-fertilised; the flowers
in this latter case being often quite sterile. We may therefore conclude
that a cross does some good, though it does not give to the crossed
seedlings increased powers of growth.
7. Viscaria oculata.
The average height of the fifteen intercrossed plants to that of the
fifteen self-fertilised plants was only as 100 to 97; but the former
produced many more capsules than the latter, in the ratio of 100 to 77.
Moreover, the flowers on the parent-plants which were crossed and
self-fertilised, yielded seeds on one occasion in the proportion of 100
to 38, and on a second occasion in the proportion of 100 to 58. So that
there can be no doubt about the beneficial effects of a cross, although
the mean height of the crossed plants was only three per cent above that
of the self-fertilised plants.
8. Specularia speculum.
Only the four tallest of the crossed and the four tallest of the
self-fertilised plants, growing in four pots, were measured; and the
former were to the latter in height as 100 to 98.
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