POLLINATION OF FLOWERS 
676 
13 utterfly-flowers. 
Moth-flowers. 
Fly-flowers. 
Flowers visited by miscellaneous insects. 
Insect-pollinated flowers may be divided 
into pollen flowers and nectar-flowers ac¬ 
cording as they contain nectar or only pol¬ 
len. Nectar-flowers may be divided into 
flowers with the nectar fully exposed, part¬ 
ly concealed, or deeply concealed. 
Flowers Pollinated by the Wind. —Wind- 
pollination is the oldest method of pollen 
dispei’sion and for many years the only 
method of pollination in existence. There 
were wind-pollinated cone trees as far back 
as the Devonian Age, long before the de¬ 
velopment of the higher seed plants. The 
wind offers an excellent medium for inter¬ 
crossing. It levies no toll for its services, 
and it is seldom that there is not sufficient 
air stirring to carry pollen. A gentle breeze 
is much better than a strong wind which 
sweeps the pollen away too quickly and too 
forcibly. When the weather is stormy, as 
is often the case when the wind is high, 
the anthers do not open; and, if they have 
already dehisced, they close ag*ain to pro¬ 
tect the pollen. An objection to wind- 
pollination is the great waste of pollen. 
There are no allurements to attract insects, 
such as nectar, bright colors, odors, or 
resting places. 
As has already been described, in the 
conifers and cycads the stamens and seeds 
are produced in different cones, in part of 
the species on the same tree, and in part on 
different trees. In the fir, the spruce, the 
hemlock, and the pine both kinds of cones 
are on the same tree, but the fruiting cones 
are above the cones producing the pollen, 
an arrangement favoring cross-pollination. 
In the juniper, yew, and all the cycads the 
staminate and seed cones are on different 
trees. 
The grasses, sedges, and rushes are also 
all pollinated by the wind with the excep¬ 
tion of a few cases of self-pollination. To 
the grasses belong the edible cereals, corn, 
wheat, rye, barley, oats, rice, and millet. 
“Next to the importance,” says Ingalls, “of 
the divine profusion of water, light, and 
air, those great physical facts which ren¬ 
der existence possible, may be recorded the 
universal beneficence of grass. Should its 
harvest fail for a single year, famine would 
depopulate the earth.” Many species bloom 
at dawn, just as the sun is rising above 
the horizon, when, their anthei'S loaded with 
pollen, they exhibit an attractiveness very 
different from their appearance at noon¬ 
day. The stamens and pistils often occur 
in the same flower; but self-pollination 
may be prevented by the stigmas ripening 
before the anthers. Common com is an il¬ 
lustration of a grass which has the stamens 
and pistils in separate flowers. The blos¬ 
soms that bear the seed are midway on the 
stalks, and are commonly termed the ear; 
the pistils are the silk. The flowers that 
bear the pollen are at the very summit of 
the stalk, and are known as the spindle. 
When ripe the pollen is shaken off and falls 
on the silk below, or, what is still better, 
it is wafted by the wind to the silk of neigh¬ 
boring stalks, thus preventing' inbreeding. 
Very many deciduous-leaved trees and 
bushes are wind-pollinated, as the alders, 
birches, oaks, hornbeams, elms, walnuts, 
hickories, and beeches. Usually the sta¬ 
mens and pistils are in different flowers 
either on the same plant or on different 
plants. Trees the world over more often 
have the stamens and pistils separated, and 
consequently the sexes, than herbaceous 
plants. Anemophilous or wind-pollinated 
trees bloom in early spring before the fol¬ 
iage has appeared, in order that the leaves 
may not intercept 1 and waste the pollen. 
Many coarse, homely weeds are pollin¬ 
ated by the wind, as pigweed, ragweed, net¬ 
tle, hop, pondweed, sorrel, dock, hemp, and 
rue anemone. They agree in having small, 
green or dull-colored flowers, which are 
commonly odorless, but which are produced 
in immense numbers. The pollen grains 
are round and smooth, Avhile the stigmas 
are lobed or feathery to present a large re¬ 
ceptive surface. They flourish in a great 
variety of situations and are well worthy 
of careful observation. The Roman worm¬ 
wood (Ambrosia artemisiifolia) blooms in 
the fall and is common everywhere in old 
fields and waste land. The air in the fall 
is filled with its yellow pollen, which is be¬ 
lieved to be productive of hay fever. The 
stamens of the stinging nettles are elastic; 
and, when the flowers open, they suddenly 
