-.70 



BOTANY 



PART II 



becomes filled with protoplasm in which are numerous nuclei. Each of the two 

 generative cells from the pollen-tube fuses with a female nucleus. Of all the 

 fertilised cells resulting from the penetration of a number of pollen-tubes to the 

 embryo-sac only one develops into an embryo. 



B. Angiosperms ( 8 ) 



(a) The MICROSPORES of Angiosperms before they are shed from 

 the pollen-sac form an antheridial mother cell (Fig. 549 m) which is 



D 



Fia. 549. Pollen-grain of Lilium Martagon and its germination, k, Vegetative nucleus of the 

 pollen-grain ; m, antheridial mother cell ; </, generative nuclei, (x 400. After STBASBURGKR.) 



clearly delimited from the large pollen-tube cell, but is not enclosed 

 by a cell wall. When the pollen grain germinates on the stigma the 

 antheridial cell passes into the pollen tube, and its nucleus sooner or 

 later divides into two generative nuclei (g) which lie free in the proto- 

 plasm within the pollen-tube without being enclosed in a common 

 mass of protoplasm. They are of an elongated oval or ellipsoidal 



