378 



TEXTBOOK OF BOTANY 



GRAIN COAT - 



NUCELLUS 



Fig. 169. Stages in the growth of embryo and endosperm in a developing grain 

 of corn: A, 5 days after poUination; B, 10 days; C, 13 days; D, 15 days, and E, 

 20 days after pollination. Photos by Lois Lampe. 



although none of its structures is the direct result of fertihzation. Some- 

 times structures adjacent to the ovulary also grow and form a part of 

 the fruit. 



The life cycle of a flowering plant. We have now observed the series of 

 changes in the flower known as sexual reproduction, leading directly 

 or indirectly to the formation of fruits and the different parts of the 

 seeds. If a seed is planted, a seedling may develop from the embryo. At 

 first, food used in germination and in initial growth comes from the 

 cotyledons of the embryo or from the endosperm. As soon as chlorophyll 

 is formed in the seedling, however, photosynthesis may occur, and we 

 have the usual green plant with which we are quite familiar. 



Upon further growth of the seedling and completion of the vegetative 

 stage, buds containing flower primordia develop. Through the series of 

 events we have just described, seeds are again formed. We started with 

 a seed and now another seed has been formed: this cycle may be 

 repeated indefinitely. The development from seed to seed is known as 



