SPERMATOPHYTES : GYMNOSPERMS 
351 
nc- 
n- 
pine the micropyle is directed downward, toward the base 
of the sporophyll. 
230. The gametophytes. The male and female gameto- 
phytes are so small that they develop entirely within the 
spores (pollen-grain and 
embryo-sac), and there- 
fore can only be observed 
by the microscope. 
The female gameto- 
phyte (often called " en- 
dosperm ") fills up the 
large embryo-sac, and on 
its surface toward the 
micropyle develops regu- 
lar flask-shaped arche- 
gonia (Fig. 312). 
The male gameto- 
phyte is still more re- 
duced, and is represented 
by a very few small cells 
which appear within the 
pollen - grain, two of 
which are sperm -cells. 
These sperm-cells must 
reach the archegonia, 
and accordingly the pol- FIG 312 
len-grain sends out a tube 
(pollen-tube), into which 
the sperm-cells enter, and 
are thus brought to the 
archegonia (Fig. 110). 
231. Fertilization. 
Diagrammatic section through ovule 
(megasporangium) of spruce (Picea), showing 
integument (i), nucellus (nc), endosperm or 
female gametophyte (e) which fills the large 
megaspore imbedded in the nucellus, two 
archegonia (a) with short neck (c) and venter 
containing the egg (o), and position of ger- 
minating pollen-grains or microspores (p) 
whose tubes (t) penetrate the nucellus tissue 
and reach the archegonia. After SCHIMPEK. 
Before fertilization can 
take place the pollen-grains (microspores) must be brought 
as near as possible to the female gametophyte with its arche- 
gonia. The spores are formed in very great abundance, 
