340 



REPRODUCTION IN PLANTS 



from the fertilized egg in the same manner that the ani- 

 mal arises from a fertilized egg. Since the development of 

 the animal embryo has been adequately described in the 

 last chapter it is unnecessary to repeat the story here. In 

 the development of endosperm there is cell division and 



Fio. 93. — ^ is a young ovule with the megaspore mother cell. 

 B shows the mature female gametophyte which develops from the 

 megaspore; at one end are the egg, e, and two other cells called 

 synergids, s; in the middle are two nuclei in the act of fusing together 

 to form the endosperm nucleus; and at the other end are three cells 

 which ordinarily take no further part in the development of the seed. 

 When the pollen tube reaches a female gametophyte one of its sperms 

 unites with the egg and gives rise to the young plant or embryo, 

 the other unites with the endosperm nucleus and may give rise to 

 a special tissue called endosperm, which when present contains 

 the food supply for the embryo. 



growth but little differentiation of cells beyond that in- 

 volved in food storage. Wherever abundant endosperm 

 is developed its cells are used to store a supply of starch 

 or other food for the young plant. In pines and similar 

 plants there is no endosperm and food is stored in the 

 large female gametophyte. In Flowering Plants wherever 



