PBANEBO&AMIA. 



229 



486. The mature embryo-sac is a considerable cavity con- 

 taining several rounded masses of protoplasm, one of wbicb 

 is the germ-cell. As the tissues of the ovule-body can suf- 



FiG. 180. — Diagrammatic longitudinal sections of ovules, fc, the body of the 

 ovule, with its embi'yo~sac, em; az, the outer, and ii, the inner, coat; m, the 

 opening in ovule-coat (micropyle); c, the base of the ovule; /, the ovule-stalk; 

 A^ a. straight ovule; B^ an inverted ovule; the long stalk, /, has fused with the 

 outer coat of one side of the ovule. 



ficiently nourish the germ-cell, there is little or no develop- 

 ment of the first stage (prothallium) at this time, and there 

 is an almost complete suppression of the archegone-walls. 



Fig. 131.— .4, a longitudinal section of an ovule of the Pansjr, after fertilization ; 

 a and i, coats of the ovule; p, pollen-tube; e, embryo-sac, with the very young 

 embryo at one end and free endosperm-cells at the other. B, apex of erabiyo- 

 sac, e; eb, very young embryo of four cells. 



487. Fertilization takes place as follows: The pollen- 

 cell, resting upon the moist surface of the stigma, germi- 

 nates, and its tube penetrates the soft tissues of the stigma 

 and style, finally reaching the cavity of the ovary, where 



