SPERMATOCYTES : GYMNOSPERMS 



351 



no 



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- 

 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. — 

 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, 



Fig. 312. Diagrammatic section through ovule 

 (megasporangium) of spruce (Mcea), showing 

 integument (f), 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 (7) penetrate the nucellus tissue 

 and reach the archegonia. — After Schimpeb. 



