This sterility was not due to the injurious
effects of the net, for I fertilised five flowers with pollen from an
adjoining plant, and these all yielded fine seeds. I removed the net,
whilst one little branch still bore a few not completely faded flowers,
and these were visited by bees and yielded seeds.
Salvia coccinea.--Some covered-up plants produced a good many fruits,
but not, I think, half as many as did the uncovered plants; twenty-eight
of the fruits spontaneously produced by the protected plant contained on
an average only 1.45 seeds, whilst some artificially self-fertilised
fruits on the same plant contained more than twice as many, namely 3.3
seeds.
Bignonia (unnamed species) (Bignoniaceae).--Quite sterile: see my
account of self-sterile plants.
Digitalis purpurea (Scrophulariaceae).--Extremely sterile, only a few
poor capsules being produced.
Linaria vulgaris (Scrophulariaceae).--Extremely sterile.
Antirrhinum majus, red var. (Scrophulariaceae).--Fifty pods gathered
from a large plant under a net contained 9.8 grains weight of seeds; but
many (unfortunately not counted) of the fifty pods contained no seeds.
Fifty pods on a plant fully exposed to the visits of humble-bees
contained 23.1 grains weight of seed, that is, more than twice the
weight; but in this case again, several of the fifty pods contained no
seeds.
Antirrhinum majus (white var.
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