POLLINATION OF FLOWERS 
670 
the eggs and the dispersal of only one kind 
of spore greatly reduced the waste of 
spores. The seed also proved a great ad¬ 
vantage in providing for the distribution 
of the species. 
Pollination and the habit of forming 
seeds arose at the same time; and, as there 
were cone trees as far back as the Devon¬ 
ian Age, the origin of both is very ancient. 
Pollination consists in carrying pollen to 
the ovules of the cone trees (Gymno- 
sperms), and to the stigmas of the flower¬ 
ing plants (Angiosperms). It is thus re¬ 
stricted to the seed plants, but its beginning 
goes back to the ferns. 
THE FOLLINATION OF THE CONE TREES OR 
GYMNOSPERMS. 
The Gymnosperms include the Cycads 
(Cycadaceae), the conifers (Coniferae), 
and a small peculiar group called the joint 
firs (Gnetaceae). There are about 100 spe¬ 
cies of cycads, 300 species of conifers and 
46 species of joint firs. The cycads occur 
in the tropics of both the Old and New 
Worlds; but the conifers are found chiefly 
in the north and south temperate zones, 
where they form extensive forests. The 
cycads resemble tree-ferns and palms, the 
tallest species attaining a height of 40 to 
60 feet. The conifers have needle-like leaves 
and include the giant firs, spruces, red¬ 
woods, and Sequoias of the Pacific Coast, 
among the largest trees in the world. 
In the cycads and conifers the stamens 
and ovules are in separate cones, formed of 
numerous scales spirally arranged around 
a central axis. As the seeds are unpro¬ 
tected by a seed-case, the purpose of the 
cone of scales is to protect them from the 
weather; and so great is its advantage that 
the conifers may owe their existence to it. 
In the cycads the ovules and stamens are 
in separate cones on different trees. In the 
conifers (Coniferae) the stamens and seed 
cones are in many species on the same 
tree, as in the fir, spruce, and pine, or on_ 
different trees as in the juniper and yew. 
The seed cones are at the top of the tree 
or at the end of the branches, while the 
staminate cones are lower down on the lat¬ 
eral branches, an arrangement favoring 
cross-pollination. The seed cones may be 
of great size; in the cycad Dioon spinulo- 
sum of Mexico its length is 20 inches and 
its weight 33 pounds. 
When the evergreen forests of the tem¬ 
perate zone bloom in May the neutral-col¬ 
ored cones are seldom noticed, as they do 
not usually contrast strongly with the green 
needle-like leaves. But a red pine cov¬ 
ered with red-purple staminate cones, half 
an inch in length, and associated in clus¬ 
ters of 30 or more; and a black spruce and 
balsam fir bearing innumerable staminate 
cones, about the size and color of a field 
strawberry, certainly present a strikingly 
handsome appearance. The fertile cones 
are much less noticeable, but they are pur¬ 
ple in the spruce and pale green in the fir. 
The seed cones of the cycads are often 
brilliantly colored, as orange-colored scales 
and scarlet seeds. None of the cones yield 
nectar, and the bright colors are an inci¬ 
dental result of no advantage in pollina¬ 
tion. 
All of the cycads and conifers are wind- 
pollinated. The quantity of pollen pro¬ 
duced is almost incredible. Clouds of pol¬ 
len rising from pine trees are sometimes 
mistaken for columns of smoke. The fall¬ 
ing of pollen grains in such immense num¬ 
bers that they tinge the ground yellow has 
given rise to reports of sulphur showers. 
The pollen is very light and in the pine is 
provided with two bladder-like wings, which 
greatly increase its buoyancy, and cause 
it to be carried upward by a slight breeze 
to the seed cones at the apex of the tree. 
On the upper side of each of the scales of 
the fertile cones there are two naked ovules 
in the end of which there is a small open¬ 
ing, the micropyle or little gate. The mi- 
cropyle is wide open, and filled with a drop 
of mucilage well shown in the yew and 
running juniper. When the air is filled 
with pollen slowly settling downward, pow¬ 
dering the foliage, the grass and the 
ground, it can not fail to come in contact 
with the drop of mucilage. As this gradu¬ 
ally dries up the pollen grains* are drawn 
into the »ovule until they come in contact 
with the spore containing the egg. The 
grain of pollen then puts out a tube, which 
enters the spore and from which there is¬ 
sues a sperm which unites with the egg. 
In the pine this tube grows so slowly that 
fertilization does not take place for over 
a year after pollination. Cross-pollination 
