I fertilised a few flowers on a plant growing
almost in a state of nature with pollen from another plant close
alongside, and the four crossed capsules contained on an average 9.2
seeds. This large number no doubt was due to the bush being covered up,
and thus not exhausted by producing many pods; for fifty pods gathered
from an adjoining plant, the flowers of which had been fertilised by the
bees, contained an average of only 7.14 seeds. Ninety-three pods
spontaneously self-fertilised on a large bush which had been covered up,
but had been much agitated by the wind, contained an average of 2.93
seeds. Ten of the finest of these ninety-three capsules yielded an
average of 4.30 seeds, that is less than half the average number in the
four artificially crossed capsules. The ratio of 7.14 to 2.93, or as 100
to 41, is probably the fairest for the number of seeds per pod, yielded
by naturally-crossed and spontaneously self-fertilised flowers. The
crossed seeds compared with an equal number of the spontaneously
self-fertilised seeds were heavier, in the ratio of 100 to 88. We thus
see that besides the mechanical adaptations for cross-fertilisation, the
flowers are much more productive with pollen from a distinct plant than
with their own pollen.
Eight pairs of the above crossed and self-fertilised seeds, after they
had germinated on sand, were planted (1867) on the opposite sides of two
large pots.
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