24 The Third and Fourth Generation 



of the ovule has also changed ; it has developed 

 nutritive material and tough coats about the 

 plantlet, and so has helped form the seed. The 

 ovary enlarges and possibly unites with other 

 floral parts to form the fruit (Fig. 4). In 

 shelling peas one often sees within the pod, in 



Fig. 4. — -Pistil of mandrake enlarging to form the fruit; cross- 

 section at the right. 



addition to the fully developed peas, some tiny 

 objects, each attached where you would expect 

 a pea to grow; but these are not so large as 

 the head of a pin. Such are ovules containing 

 eggs that failed to develop because of the lack 

 of adequate fertilization. 



It is difficult to watch the egg develop into 

 the embryo in the plant, for it is hidden in the 



