FERTILIZATION. 



177 



(Chapter III., Introduction). This delicate tube pro- 

 longs itself downward till it reaches the ovary, enter- 

 ing it ; comes in contact with 

 the ovule, which it penetrates, 

 and discharges the proto- 

 plasm of the pollen grain 

 upon the protoplasm of the 

 germ cell, or ovule, and thus 

 fertilizes it. The protoplasm 

 of the two cells having min- 

 gled, the ovule ripens into a 

 seed, in which resides the 

 embryo of a new plant. 



The quantity of proto- 

 plasm in the ovule or germ 

 cell is greater than that con- 

 tained in the pollen grain. 



435. Gamogenesis (Greek 

 ydpog, marriage, yeveais, pro- 

 duction). Formation by mar- 

 riage is the name applied to 

 this mode of fertilization. 



529, Section of the ovary of Polygonum Penn- 



436. Conjugation iS the sylvanicum, in process of fertilization. (Magni- 

 fied 20 diameters.) c, Natural size; n, one of the 



Of another mode Which stamens . having discharged its pollen ; , a grain 



of pollen and its tube; s, styles and stigmas; o, 



3mpHshed bV the Union ovar y> ovule < ml>ry sac containing the embry- 

 onic globule. The extremity of a pollen-tube is 

 Of tWO Similar CellS Side by seen in contact with the embryo sac. 



side, the combination resulting in a germinating cell. 



437. The ovule fertilized becomes a new center of 

 growth. First it expands to a proper cell, attached to 

 the wall of the sac near the micropyle. It then, by 

 division and subdivision, multiplies itself, and begins to 

 take form according to the species, showing cotyledon, 

 plumule, etc., until fully developed into the embryo. 



IS 



