336 REPRODUCTION IN PLANTS 



in order to understand reproduction in flowering plants. 

 The Ovule and Female Gametophyte (Fig. 90). — 

 The ovule actually corresponds to the organ (sporangium) 

 on the back of a fern leaf in which the spores are pro- 

 duced. When the development of the ovule is carefully 

 studied it is found that at a certain stage there is devel- 

 oped a spore mother cell and that it undergoes two succes- 

 sive divisions exactly comparable to those described in 

 Chapter XXVI for the maturation of the animal egg, and 



Fio. 90. — The Ovule and Female Ciamctophyte. A, shows a cross 

 section thronph the ba.se of the pistil of a lily flower. There are 

 three ravities, in each of which are two vertical rows of ovules. 

 The figure .shows .six ovules, each containing a nearly mature female 

 gametophyte. 



which will be presently described for plant pollen. These 

 two divisions result in four spores, only one of which sur- 

 vives and matures. The other three remain small and are 

 eventually crushed and destroyed. The one functional 

 spore develops into a small female gametophyte without 

 ever being shed from the ovule. It is the fact that the 

 spore is not shed on the ground as it is in the ferns, and 

 that the gametophyte is small enough to be retained in 



