VEGETATION. 141 



to plant-juice (latex), and organizing into its own structure ac- 

 cording to its own plan. The vital phenomena on which these 

 transformations depend are called absorption, circulation, exhala- 

 tion, assimilation, secretion, all of which processes take place in 

 the individual cell. Cell-life, therefore, is an epitome of the life 

 of the whole plant. The cell is never a spontaneous production ; 

 it is the offspring of a p^e-existing cell. So with the plant ; it is 

 always the offspring of a pre-existing embryo or cell. Nothing 

 but a cell can produce or nourish a cell. 



440. Two kinds of organic matter make up the cell. The first, 

 protoplasm, or protein (C 40 H 31 13 N 5 ), the material of the pri-< 

 mordial utricle ( 373), etc., containing nitrogen; 2d, cellulose 

 (C 12 H 10 10 ). the material of the outer wall or crust, etc., con- 

 taining no nitrogen. The former more nearly resembles animal 

 matter, and is the sea-t of the 



vital force and chemical action. (jjjj:, 



441. Through the invisible ^ 

 pores of its walls the cell im- 4jf 

 bibes the fluid in which its food f^ 

 is dissolved, viz., sugar or dex- 519 



trine, ammonia Or SOme Other 519, Protococcusviridis-the Green Snow-plant. 



520, 1'euicillum glaucum the Yeast-plant. 



nitrogenous substance. Such a 



fluid may be the flowing sap of the plant, or any similar artificial 

 mixture in which the cell is bathed, as (in the case of the Yeast- 

 plant) a syrup with mucilage. 



442. The sugar is thus brought into contact with the proto- 

 plasm in the cell, through whose action it is decomposed, and 

 its elements transformed into cellulose and water. Thus each 

 atom of (grape) sugar or dextrine becomes 



One atom of cellulose, C 12 H 10 10 

 and two atoms of water, H a 3 



C H u O u = grape sugar. 



The water is exhaled with the rest; the cellulose is retained to 

 incrust a new cell as soon as the primordial utricle shall next 

 divide itself to form one. Or it may be deposited as starch 

 granules for future use. 



443. In the cells of green plants the globules of chlorophyl 



