680 
POLLINATION OF FLOWERS 
than the pistils self-pollination is impos¬ 
sible. The veryt existence, therefore, of the 
yuccas depends on the little moths of Pro¬ 
nub, a. Soon after twilight falls the moth 
flies from flower to flower, and alone of all 
the thousands of moths in the world gathers 
a ball of pollen. Then she lays her eggs 
in the seed-vessel, after which she climbs 
the pistil, and stuffs the ball of pollen into 
the hollow formed by the stigmas. Appar¬ 
ently she deliberately pollinates the flow¬ 
ers in order that they may produce seed. 
If she failed to perform this service to the 
plant her offspring would perish for want 
of food. While this almost incredible act 
of pollination is probably the result of in¬ 
stinct not intelligence, its origin is very 
difficult of explanation. 
There are about 100 species of hawk- 
moths in this country. They are distin¬ 
guished by their swift impetuous flight, 
their size and sombre but handsome garb 
of tan, brown, and gray colors. As flower 
pollinators they easily surpass all other 
moths and the butterflies. The rapidity of 
their flight is astonishing, and a species of 
Macroglossa has been seen to visit several 
hundred flowers in a few minutes. Com¬ 
mon hawk-moth flowers are the climbing 
honeysuckle, the evening species „ of to¬ 
bacco, thorn apple, the white lilies, several 
species of gentians and orchids, and the 
sweet-scented Gardenia. Nocturnal flowers 
are usually white or yellow, as blue and red 
would be nearly invisible in the evening 
shadows. 
Bee-Flowers .—As pollinators of flowers 
the bees far surpass all other insects. Un¬ 
like all other insects they feed their brood 
with pollen, and they are thus wholly de¬ 
pendent on flowers for food both for them¬ 
selves and their young. As the result of 
their great industry and mental acuteness 
there have been developed thousands of 
flowers which are adapted to their visits 
and are in consequence called “bee-flowei’s.” 
They have the nectar deeply placed where 
it cannot readily be pillaged by ants, 
beetles, and flies, and are often irregular 
in form. (The purpose of these odd and 
and sometimes bizarre forms is to compel 
the bee to pursue a fixed path to the nec¬ 
tar, so that pollination may be effected 
with greater certainty.) Finally they are 
very often blue or red in color. 
The legume family, or Legiuninosae, in¬ 
cludes a great number of common bee- 
flowers, as the pear, bean, locust, alfalfa, 
clover, vetch, red-bud, partridge pea, sain¬ 
foin, lupine, and sweet clover. The flowers 
bear a crude resemblance to a butterfly, as 
in the sweet pea. For the most part nine of 
the ten stamens unite to form a tube at the 
bottom of which lies the nectar. Four of 
the petals interlock around this tube, while 
the fifth, called the standard, is broad and 
erect and brightly colored to attract the 
attention of insects. The two lower petals 
enclosing the stamens form the keel or 
carina, and the two lateral petals are termed 
the wings. In order to obtain the nectar a 
bee rests on the two wing-petals, braces its 
head against the standard, thus pushing 
downward the keel, and exposing the open¬ 
ing in the staminal tube. When the keel is 
pressed downward, the pollen is placed on 
the under side of the bee’s body in four 
different ways. 
1. Elastic apparatus: The stamens and 
the pistil project from the keel as long as 
the bee remains on the flower, and then re¬ 
turn within the keel, as in sweet clover, 
white clover, alsike clover, and sainfoin. 
2. Explosive apparatus: The stamens 
and pistil suddenly spring out of the keel 
but never return within it, as in alfalfa 
and tick-trefoil. Only one effective visit is 
possible. 
3. Pumping apparatus. A small amount 
of pollen is pumped out of the end of the 
keel, each time a bee pushes it down, by 
the thickened ends of the stamens, as in 
the lupine. 
4. Brushing apparatus: A brush of hairs 
on the pistil sweeps out a small amount of 
pollen from the tip of the keel, as in the 
pea, bean, locust, and vetch. 
In the mint family (Labiatae) and the 
figwort family (Scrophulariaceae) there 
are many two-lipped bee-flowers. The lar¬ 
ger flowers often mimic the heads of rep¬ 
tiles, animals or inanimate objects, as in 
the turtlehead, monkey-flower, snapdragon, 
toadflax, foxglove, slioe-flower, scullcap, 
painted cup, and dragonhead. In these flow¬ 
ers the stamens and pistil lie under the up¬ 
per lip, and the pollen is placed on the back 
