The insect _visits the flower for the nectar_ (for the making of
honey) _and may unknowingly carry the pollen_. Spurs and sacs in the
flower are =nectaries= (Fig. 200), but in spurless flowers the nectar
is usually secreted _in the bottom of the flower cup_. This compels
the insect to pass by the anther and rub against the pollen before
it reaches the nectar. Sometimes the anther is a long lever poised
on the middle point and the insect bumps against one end and lifts
it, thus bringing the other end of the lever with the pollen sacs
down on its back. Flowers that are pollinated by insects are said to
be =entomophilous= (“insect loving”). Fig. 200 shows a larkspur. The
envelopes are separated in Fig. 201. The long spur at once suggests
insect pollination. The spur is a sepal. Two hollow petals project
into this spur, apparently serving to guide the bee’s tongue. The two
smaller petals, in front, are peculiarly coloured and perhaps serve
the bee in locating the nectary. The stamens ensheath the pistils
(Fig. 202). As the insect stands on the flower and thrusts its head
into the centre, the envelopes are pushed downward and outward and
the pistil and stamens come in contact with its abdomen. Since the
flower is proterandrous, the pollen that the pistils receive from the
bee’s abdomen must come from another flower. Note a somewhat similar
arrangement in the toadflax or butter-and-eggs.
[Illustration: FIG. 202.—STAMENS OF LARKSPUR, surrounding the
pistils. ]
In some cases (Fig. 203) the stamens are longer than the pistil in
one flower and shorter in another. If the insect visits such flowers,
it gets pollen on its head from the long-stamen flower, and deposits
this pollen on the stigma in the long-pistil flower. Such flowers are
=dimorphous= (of two forms). If pollen from its own flower and from
another flower both fall on the stigma, the probabilities are that
the stigma will choose the foreign pollen.
[Illustration: FIG. 203.—DIMORPHIC FLOWERS OF PRIMROSE.]
_Many flowers are pollinated by the wind._ They are said to be
=anemophilous= (“wind loving”). Such flowers produce great
quantities of pollen, for much of it is wasted. They usually have
broad stigmas, which expose large surfaces to the wind. They are
usually lacking in gaudy colours and in perfume. Grasses and pine
trees are typical examples of anemophilous plants.
[Illustration: FIG. 204.—FLOWERS OF BLACK WALNUT: Two Pistillate
flowers at _A_, and staminate catkins at _B_.]
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