FERTILIZATION 



137 



tube then enters into the embryo-sac and emits one 

 of the generative cells, the other generating cell and 

 the vegetative cell having been disorganized in the 

 meantime. The generative cell, guided by the syner- 

 gidae, comes into contact with the oosphere and com- 

 pletely fuses with it, nucleus with nucleus, and proto- 

 plasm with protoplasm, giving rise to a single cell 

 known as oospore. This process of the formation of 

 the oospore by the union of the male and the female 

 element is known 



as FERTILIZATION. 



After fertilization 

 the oospore se- 

 cretes a cellulose 

 wall, and is now 

 a complete cell. 

 The oospore then 

 begins to grow, 

 and gives rise to 

 the embryo, with 

 its radicle, plum- 

 ule, and cotyle- 

 dons; the number 



of cotyledons being one in Monocotyledons and two 

 in Dicotyledons. The radicle always points towards 

 the micropyle. In addition, the embryo is always 

 provided with a process known as embryo-feeder or 

 SUSPENSOR. While the embryo is developing, the 

 embryo-sac is filled with a mass of cells (Jt tissue, 

 first by cell-division and subsequently by free-cell 

 formation. This tissue is known as endosperm (fig. 

 1 21). The cells of the endosperm become the store- 

 house of food-materials, such as starch, oils, pro- 

 teids, &c. The cells of the nucellus also become 

 filled with similar substances, and the nucellus is now 



Fig:. 121. — Ovule after Fertilization 



S, Embrj'o-sac with developing endosperm. 

 E, Embryo (after Prantl and Vines). 



