i68 



Introduction to Botany. 



plastids, the nucleus making up by far the greater part of 

 the sperm protoplast, while the egg is relatively rich in 

 cytoplasm. Here we have evidence that the nucleus in 



particular is the bearer 

 of the inheritable quali- 

 ties, since the offspring 

 may inherit more of the 

 peculiarities of the plant 

 furnishing the sperm 

 than of the plant bear- 

 ing the egg. 



121. Result of Fertili- 

 zation. After the egg 

 has been fertilized it 

 forms a wall about it- 

 self, and begins a series 

 of cell divisions which 

 result in the formation 

 of the embryo, with 

 which we have already 

 become acquainted in 

 our study of seeds. At the 'same time, within the embryo 

 sac other cells are being produced which become gorged 

 with food materials. This food-bearing tissue is called the 

 endosperm. The reserve food remains either entirely out- 

 side of the embryo, as in the case of the castor bean, or 

 it may become absorbed by the cotyledons about as fast 

 as it is produced, as illustrated by the Lima bean ; or it 

 may be only partly absorbed by the embryo, as in Indian 

 corn. 



The fertilization of the egg stimulates not only the 

 growth of the embryo and the accumulation of reserve 

 food, but it also incites the growth of the ovule as a whole 



FIG. 89. 



Showing the fusion of the nuclei of the Sperm 

 and of the Egg cell.. /, the pollen tube ; h, the 

 egg cell ; u, the coalescing of sperm and egg 

 nuclei which is the essential process of the 

 fertilization of the egg. 



