passage is narrow, and is roofed over by the column, so that a bee, in
forcing its way out, first rubs its back against the viscid stigma and then
against the viscid glands of the pollen-masses. The pollen-masses are thus
glued to the back of the bee which first happens to crawl out through the
passage of a lately expanded flower, and are thus carried away. Dr. Cruger
sent me a flower in spirits of wine, with a bee which he had killed before
it had quite crawled out, with a pollen-mass still fastened to its back.
When the bee, thus provided, flies to another flower, or to the same flower
a second time, and is pushed by its comrades into the bucket and then
crawls out by the passage, the pollen-mass necessarily comes first into
contact with the viscid stigma, and adheres to it, and the flower is
fertilised. Now at last we see the full use of every part of the flower,
of the water-secreting horns of the bucket half-full of water, which
prevents the bees from flying away, and forces them to crawl out through
the spout, and rub against the properly placed viscid pollen-masses and the
viscid stigma.

The construction of the flower in another closely allied orchid, namely,
the Catasetum, is widely different, though serving the same end; and is
equally curious. Bees visit these flowers, like those of the Coryanthes,
in order to gnaw the labellum; in doing this they inevitably touch a long,
tapering, sensitive projection, or, as I have called it, the antenna. This
antenna, when touched, transmits a sensation or vibration to a certain
membrane which is instantly ruptured; this sets free a spring by which the
pollen-mass is shot forth, like an arrow, in the right direction, and
adheres by its viscid extremity to the back of the bee. The pollen-mass of
the male plant (for the sexes are separate in this orchid) is thus carried
to the flower of the female plant, where it is brought into contact with
the stigma, which is viscid enough to break certain elastic threads, and
retain the pollen, thus effecting fertilisation.