THE VOI-ATILE PAST OF PLANTS. 41 



On account of their abundance and uses the Carbhy- 

 drates rank as the most important class of vegetable sub- 

 stances. Their name refers to the fact that they consist 

 . of Carbon, Hydrogen and Oxygen, the last two elements 

 being always present in the same proportions that are 

 found in water. 



These bodies, especially cellulose and starch, form by 

 far the larger share — perhaps seven-eighths — of all the dry 

 matter of vegetation, and most of them are distributed 

 throughout all parts of plants. 



a. The Amylases. 



Cellulose (C6Hio06)n. — Every agricultural plant is 

 an aggregate of microscopic cells, i. e., is made up of 

 minute sacks or closed tubes, adhering to each other. 



Fig. 10 represents an extreinely"thin slice from the stem of a cabbage, 

 magnified 230 diameters. The united walls of two cells are seen in sec- 

 tion at a, while at 6 an empty space is noticed. 



Fig. 10. 



The outer coating, or wall, of the vegetable cell con- 

 sists chiefly or entirely of cellulose. This substance is 

 accordingly the skeleton or framework of the plant, and 

 the material that gives toughness and solidity to its parts. 

 Next to water it is the most abundant body in the vege- 

 table world.' 



