CHAPTER VI. 



FERTILIZATION. 



SELECTIVE POWER OF PLANTS FORM IN WHICH FOOD IS TAKEN UP 



EXCRETION — CIRCULATION OF THE SAP — ORGANIC SUBSTANCES : 



OXYGEN, HYDROGEN, CARBON, NITROGEN INORGANIC SUBSTANCES 



MANURES ADAPTED TO DIFFERENT SOILS : TO CLAYS, TO PEATY SOILS, 

 TO SANDY LANDS PLANTS TO BE USED IN GREEN-MANURING APPLI- 

 CATION OF MANURES. 



"OLANTS, like animals, show a preference in the 

 selection of their food. They reject some sub- 

 stances, and elect others adapted to their nourish- 

 ment. 



Their food is supplied in two forms — liquid and 

 gaseous. It has been stated by some writers that 

 the former is absorbed by the roots, and the latter 

 exclusively by the leaves. While this in the main 

 is in accordance with observation, yet the roots do 

 also absorb gaseous food, often in considerable quan- 

 tities, especially in a well pulverized and thoroughly 

 drained soil. 



The cells through which the sap flows are, in 

 their original and simplest form, cellulose, or par- 

 enchyma. Toward the root, the sap in these cells 

 is thin ; but at the leaves it becomes thickened by 

 the decomposition of its water and the elimination 



