52 GENERAL BOTANY 



accumulate. This water and the substances sugar, acids, and 

 salts which diffuse into it from or through the cytoplasmic 

 sac are together called the cell sap. In the cells of the sugar 

 beet, sugar is the main constituent of the cell sap, while in fruits 

 both sugar, acids, and salts are found in considerable quantities. 

 The cell sap thus becomes a storehouse for the water and foods 

 which may be needed by the cell and the plant. 



The nucleus is also very important in the life of the cell and 

 the organism, being very closely connected with fertilization and 

 with the formation of new cells by division. The most important 

 act of fertilization seems to be the union of the nucleus of the 

 male cell or gamete with that of the female cell or gamete, while 

 the complex changes undergone by the chromatin of the nucleus 

 in cell division indicates its importance in that process. Although 

 the nucleus and cytoplasm are thus separated structurally and 

 seem to have certain specialized functions, it has been conclu- 

 sively shown that they are coworkers in the various cell activi- 

 ties and are mutually dependent upon each other for continued 

 existence. 



The following table summarizes the relations of the constituents 

 of the cell in terms of living and lifeless parts as discussed above. 



SUMMAKY 



1. Lifeless parts of plant cells : 



The cell wall: outer membranous covering of the living 



protoplast of a cell. 

 Vacuoles and cell sap : the cavities, or spaces (termed sap 



cavities) in the protoplasts of plant cells, and the contained 



cell sap, composed of water and other substances in solution 



within the vacuole. 

 Metaplasmic bodies : solid waste and food particles embedded 



in the protoplast. 



2. Living parts of plant cells : 



Protoplast : the entire living protoplasm of the cell, including 



the nucleus. 

 Cytoplasm: all protoplasm of the cell exclusive of nucleus 



and nucleolus. 



