who shall question for a moment that had
the flower been visited in its twilight or moonlight haunt the murmur of
humming wings about the blossom's throat would have attested the
presence of the flower's affinity, for without the kiss of this
identical moth the Angraecum must become extinct. No other moth can
fulfil the conditions necessary to its perpetuation. The floral
adaptation is such that the moth must force its large head far into the
opening of the blossom in order to reach the sweets in the long nectary.
In so doing the pollen becomes attached to the base of the tongue, and
is withdrawn as the insect leaves the flower, and is thrust against the
stigma in the next blossom visited. This was clearly demonstrated by
Darwin in specimens sent to him, by means of a probe of the presumable
length and diameter of the moth's tongue. Shorter-tongued moths would
fail to remove the pollen, and also to reach the nectar, and would thus
soon learn to realize that they were not welcome.

The Angraecum also affords in this long pendent nectary a most lucid
illustration of the present workings of natural selection. The normal
length of that nectary should be about eleven inches, but in fact this
length varies considerably in the flowers of different plants, this
tendency to variation in all organic life being an essential and amply
demonstrated postulate of the entire theory of natural selection. Let us
suppose a flower whose nectary chances to be only six inches in length.
The moth visits this flower, but the tip of its tongue reaches the
nectar long before it can bring its head into the opening of the tube.
This being a vital condition, the moth fails to withdraw the pollen; and
inasmuch as the pollen is usually deposited close to the head of the
moth, this flower would _receive_ no pollen upon its stigma. This
particular blossom would thus be both barren and sterile. None of its
pollen would be carried to other stigmas, nor would it set a seed to
perpetuate by inheritance its shorter nectary.

Again, let us suppose the variation of an extra long nectary, and the
writer recently saw a number of these orchids with nectaries thirteen
inches in length. The moth comes, and now must needs insert its head to
the utmost into the opening of the flower. This would insure its
fertilization by the pollen on the insect's tongue; and even though the
sipper _failed_ to reach the nectar, the pollen would be withdrawn upon
the tongue, to be