672 
POLLINATION OF FLOWERS 
er calyx nor corolla, or they are repre¬ 
sented only by scales and bristles. In the 
willows the flowers on a part of the bushes 
consist only of stamens, while on others 
they are composed only of pistils. In Jack- 
in-the-Pulpit the flowers are reduced to a 
single pistil or stamen.. 
Flowers may be modified also in another 
way by the fusion or consolidation of the 
organs. Tubular calyces and corollas, as 
in the morning glory and phlox, are 
stronger and better adapted to protect the 
nectar than those which consist of separ¬ 
ate sepals and petals. In the pulse family 
the stamens are commonly fused into 
“brotherhoods.” But fusion is nowhere so 
common as among the pistils. So long as 
they are separate, pollen must be placed 
on the stigma of each; but when they are 
consolidated, one application may serve to 
fertilize all the ovules. Clearly a flower 
like the buttercup, where all the parts are 
separate units, is more primitive .than an 
orchid, where they have coalesced to such 
an extent that it is difficult to determine 
their number. In primitive families again, 
like the buttercups, mallows, roses, and 
saxifrages, the flowers have regular forms 
and the sepals or petals are all alike; but 
in many families, which have developed 
more recently, the flowers have assumed 
strange bizarre forms as in the sweet pea, 
snapdragon, and sage. The purpose of 
these singular forms is to compel an insect 
to pursue a fixed path in its visits and thus 
effect pollination. Such flowers are the 
youngest and latest to appear in the plant 
world; the larkspur is of later origin than 
the buttercup, and the clover blossom than 
the rose. 
A flower is hermaphrodite or bisexual 
when it contains both stamens and pistils. 
Unisexual when either the stamens or pis¬ 
tils are wanting. Monoecious when the 
stamens and pistils are in different flow¬ 
ers on the same plant. Dioecious when the 
stamens and pistils are in different flowers 
on different plants. Polygamous when both 
hermaphrodite and unisexual flowers occur 
on the same plant. 
THE ADVANTAGE OP CROSS-FERTILIZATION. 
Tliruout the plant world cross-fertiliza¬ 
tion is of frequent occurrence. In the 
lower plants the male and female cells of 
different plants are often brought together 
thru the medium of water, and in the seed 
plants crossing is secured by cross-pollina¬ 
tion. It is, therefore, of the greatest im¬ 
portance and interest to inquire what bene¬ 
fits result from crossing. Otherwise the 
investigation of the pollination of flowers 
becomes a blind pursuit. Plants reproduce 
in two ways, vegetatively or without sex, 
and sexually; and contrary to the common 
belief the chief purpose of sexual repro¬ 
duction is not the multiplication of plants. 
As it originated independently many times 
among the seaweeds it was evidently nec¬ 
essary for the evolution of the plant king¬ 
dom. What advantage then is there in 
sexual reproduction, which is not found in 
vegetative multiplication. 
VEGETATIVE' REPRODUCTION. ' 
Plants multiply vegetatively, or without 
sex, by fission or self-division; by spores 
or single cells which are able to grow into 
new plants; and by bulbs, stolons, tubers, 
layering, or by the breaking up of the 
plant into fragments which become new in¬ 
dividuals. The rapidity with which one- 
celled plants and animals multiply by self¬ 
division is almost incredible. Large areas 
of snow are reddened in a single night by 
a red alga. Some species of Euglena and 
Astasia are so prolific that they color the 
waters in which they live green or red. 
Other forms of Flagellata are known as 
“sea-lights,” because in darkness they emit 
light, and they often exist in such enor¬ 
mous quantities that the surface of the sea 
is illuminated for miles. According to Cohn 
the descendants of a single hay bacillus in 
24 hours equal seven septillions. Even 
more impressive of the enormous product¬ 
iveness of one-celled organisms are their 
fossil remains. The most vivid imagination 
would hardly suppose that they had been 
instrumental in building up the rock strata 
of the earth. Yet the lofty white chalk 
cliffs of southern England are composed of 
the empty shells of Forminifera mixed with 
the silicious shells of diatoms. In the In¬ 
dian Ocean the mountainous Nicobar Isl¬ 
ands are built up of flinty shells of Radio- 
laria. As island and continent builders 
these little unicells surpass all other forms 
of life, and today in the abyssmal depths 
