Plants thus circumstanced will commonly
have been intercrossed by insects; so that the seedlings which were
first experimented on will generally have been the product of a cross.
Consequently any difference in the fertility of their flowers, when
crossed and self-fertilised, will have been caused by the nature of the
pollen employed; that is, whether it was taken from a distinct plant or
from the same flower. The degrees of fertility shown in Table 9/F, were
determined in each case by the average number of seeds per capsule,
ascertained either by counting or weighing.
Another element ought properly to have been taken into account, namely,
the proportion of flowers which yielded capsules when they were crossed
and self-fertilised; and as crossed flowers generally produce a larger
proportion of capsules, their superiority in fertility, if this element
had been taken into account, would have been much more strongly marked
than appears in Table 9/F. But had I thus acted, there would have been
greater liability to error, as pollen applied to the stigma at the wrong
time fails to produce any effect, independently of its greater or less
potency. A good illustration of the great difference in the results
which sometimes follows, if the number of capsules produced relatively
to the number of flowers fertilised be included in the calculation, was
afforded by Nolana prostrata.
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