126 



-VEGETABLE HISTOLOGY. 



wall of cellulose, a substance composed of carbon, hydrogen and 

 oxygen in the proportion represented by the formula C 6 H 10 5 , 

 though in all probability the true formula of its molecule is more 

 complex than this, containing two, three or more times this 

 number of atoms of each element. 



Fig. 361. — Represents a parenchyma cell, greatly magnified, to show the parts, a, the 

 cell-wall; b, the middle lamella; c, the ectoplasm; d, endoplasm; e, vacuole; /, nucleus; 

 g; chlorophyll corpuscle; /*, intercellular space; i, protoplasmic thread. 



In mature cells aggregated to form tissues, the common cell- 

 wall between adjacent cells consists of two similar portions sep- 

 arated from each other by a substance of slightly different 

 chemical composition, and more soluble in re-agents than the 

 rest of the wall, called the middle lamella, Fig. 361, b, and at 

 the angles where the cells join are usually found small, angular 

 intercellular spaces, Fig. 361, h. ' Interior to the cell-wall is the 

 living matter of. the cell, the protoplasm, together with cell-sap, 

 and products of various kinds, which are the results of the 

 activity of the cell. 



