When the Bee pushes its proboscis down the tube (Fig. 11) it presses the
lower arm to one side, and the upper arm consequently descends, tapping
the Bee on the back, and dusting it with pollen. When the flower is a
little older the pistil (Fig. 9, _p_) has elongated so that the stigma
(Fig. 10, _st_) touches the back of the Bee and carries off some of the
pollen. This sounds a little complicated, but is clear enough if we take
a twig or stalk of grass and push it down the tube, when one arm of each
of the two larger stamens will at once make its appearance. It is one of
the most beautiful pieces of plant mechanism which I know, and was first
described by Sprengel, a poor German schoolmaster.

SNAPDRAGON

At first sight it may seem an objection to the view here advocated that
the flowers in some species--as, for instance, the common Snapdragon
(Antirrhinum), which, according to the above given tests, ought to be
fertilised by insects--are entirely closed. A little consideration,
however, will suggest the reply. The Snapdragon is especially adapted
for fertilisation by Humble Bees. The stamens and pistil are so
arranged that smaller species would not effect the object. It is
therefore an advantage that they should be excluded, and in fact they
are not strong enough to move the spring. The Antirrhinum is, so to
speak, a closed box, of which the Humble Bees alone possess the key.

FURZE, BROOM, AND LABURNUM

Other flowers such as the Furze, Broom, Laburnum, etc., are also opened
by Bees. The petals lock more or less into one another, and the flower
remains at first closed. When, however, the insect alighting on it
presses down the keel, the flower bursts open, and dusts it with pollen.

SWEET PEA

In the above cases the flower once opened does not close again. In
others, such as the Sweet Pea and the Bird's-foot Lotus, Nature has
been more careful. When the Bee alights it clasps the "wings" of the
flower with its legs, thus pressing them down; they are, however, locked
into the "keel," or lower petal, which accordingly is also forced down,
thus exposing the pollen which rubs against, and part of which sticks
to, the breast of the Bee. When she leaves the flower the keel and wings
rise again, thus protecting the rest of the pollen and keeping it ready
until another visitor comes. It is easy to carry out the same process
with the fingers.

[Illustration: Fig. 12. Fig. 13.

Flower and Pollen of Primrose]

P