98 



HISTOLOGICAL BOTANY. 



"When the cell is young, the protoplasm fills the whole 

 cavity ; but in the course of growth small drops of the 

 cell-sap appear and increase gradually in number until they 

 finally coalesce into one large mass, while the protoplasmic 

 layer, on the contrary, becomes thinner and thinner. 



Fig. 110. 



Fig. 110. — Parenchymatous cells from the leaf of the Negi 



(Allium fistulosum). n Nucleus; p protoplasm; 



s cell-sap ; w cell- wall. 



There are some cells which are not provided with cell- 

 walls ; these are termed Primordial Cells. 



Parts of the cell 



Cell-wall. 

 Protoplasm. 

 Nucleus. 

 V Cell-sap. 



1. THE CELL-WALL. 



■ The Cell-wall is the outer membrane of the cell, and 

 consists of cellulose (a carbohydrate), water, and ash-consti- 

 tuents. It is usually colorless and transparent. 



