REPRODUCTION BY SEED 163 
—is formed inside a large cell—the embryo-sac, which 
is developed in the tissues of the ovule. The egg 
always remains where it is formed, and therefore the 
male cell must be brought to it. In the higher seed- 
plants—the Angiosperms (Gr. angios, a vessel ; sperma, 
seed)—the ovules are enclosed in the ovary, and the 
pollen-grains can be brought no nearer to the ovules 
than the stigma. In the lower group of seed-plants—~ 
the Gymnosperms 
(Gr. gymnos, naked), 
pines, firs, cypresses, 
larches, yews — the 
ovules are not en- 
closed, but lie ex- 
posed to the air. In 
this case the pollen 
can be borne direct 
to the entrance of 
the ovule. The first 
step in the produc- 
tion of seed is the 
conveyance of the 
pollen to the stigma 
of the pistil, or in 
the case of Gymno- 
sperms to the ovule 
itself. This is termed 
pollination. When 
the pollen - grain is 
a 
Fie. 66.—Dr1acram or Fuownr at Time 
OF FERTILIZATION. (AFTER PRANTL AND 
VINES. ) 
a, calyx ; b, corolla ; c, stamens ; d, anther ; 
deposited upon the 
stigma it germinates. 
A long thread - like 
tube grows out of 
e, pollen-grains ; /, tube of germinating 
pollen-grain ; g, stigma; h, style ; 7, ovary; 
k, micropyle of ovule ; 7, egg-cell ; m, em- 
bryo-sac ; n, integument of ovule; 7, re- 
ceptacle. 
the grain, penetrates 
the style, and makes its way towards the ovule. The 
body of the ovule within which the egg is formed is sur- 
rounded by one or two coats, but a hole, or pore, is left in 
the coats—the micropyle (Gr. mikros, small ; pyle, gate)— 
which affords a passage to the interior. On entering the 
ovary, the growth of the pollen-tube is directed towards 
the lips of the micropyle. A liquid secreted at the 
micropyle attracts in some way the elongating tube. 
The tip of the tube enters the ovule, and, reaching 
