248 



General Botany 



Figs. 153 and 154. Cross-sections of ovules. At the left, megaspore of lily ; note the 

 surrounding nucellus and two integuments making up the ovule. At the right, the first 

 division in the megaspore (embryo sac), resulting in two nuclei. 



ding of the pollen, (3) pollination, or transfer of pollen to the 

 stigma, (4) germination and formation of the pollen tube, 

 (5) growth of the pollen tube into the ovule, and (6) movement 

 of the sperms to the end of the pollen tube. 



Development of the egg in the ovule. Inside the ovule a 

 parallel series of cell activities is going on which results in the 

 production of the embryo sac and the egg, or female gamete. 



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Figs. 155 and 156. Cross-sections of ovules. At the left the second division in the 

 embryo sac, resulting in four nuclei. At the right, the eight-celled stage of the em- 

 bryo sac ; two nuclei are about to unite to form the fusion nucleus. 



