Examine a jewel-weed blossom to see
that the clumsy bumblebee's pollen-laden back is not so likely to
come in contact with the short five-parted stigma concealed
beneath the stamens, as a hummingbird's slender bill that is
thrust obliquely into the spur while he hovers above.
But, as if the plant had not sufficient confidence in its
visitors to rely exclusively on them for help in continuing the
lovely species, it bears also cleistogamous blossoms that never
open - economical products without petals, which ripen abundant
self-fertilized seed (see white wood sorrel). It is calculated
that each jewel-weed blossom produces about two hundred and fifty
pollen grains; yet each is by no means able to produce seed in
spite of its prodigality. Nevertheless, enough cross-fertilized
seed is set to save the species from the degeneracy that follows
close inbreeding among plants as well as animals. In England,
where this jewel-weed is rapidly becoming naturalized, Darwin
recorded there are twenty plants producing cleistogamous flowers
to one having showy blossoms which, even when produced, seldom
set seed.
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