SECRETARY'S REPORT. 143 



Tlie organic part of plants consists of four elementary bodies, 

 known by tbe names of carbon, hydrogen, oxygen and nitrogen. 

 For the nature of which and confirmation of statements relat- 

 ing to agricultural chemistry see Johnston's Catechism of Agri- 

 cultural Chemistry, with an Introduction by John P. Norton. 

 The inorganic part of plants contains from eight to ten dif- 

 ferent substances, viz., potash, soda, lime, magnesia, oxide of 

 iron, oxide of manganese, silica, chlorine, sulphuric acid or oil 

 of vitriol and phosphoric acid, which for convenience may be 

 divided into three classes, alkalies, acids and neutrals. All 

 plants require constant supplies of food in order that they may 

 live and grow, which supplies they obtain partly from the air 

 and partly from the soil : organic food to support their organic 

 part,. which they take by their leaves from the air and by their 

 roots from the soil. " Some leaves have as many as one hun- 

 dred and seventy openings or mouths in a square inch." The 

 leaf of a plant seems to have three offices, power of absorption, 

 that of assisting in the chemical preparation of the sap or life 

 of the plants and that of evaporating its water. Hence we 

 find that plants which are well exposed to the sun's rays make 

 the most rapid growth. 



They obtain their inorganic food from the soil alone. A soil in 

 which plants will grow consists also of an organic or combusti- 

 ble and of an inorganic or incombustible part. The organic is 

 derived from the roots and stems of decayed plants and from 

 the dung and remains of animals and insects of various kinds. 

 A rich soil contains about one-twentieth of its weight in organic 

 matter. This organic matter supplies the organic food which 

 plants draw from the soil through their roots. It necessarily 

 diminishes when the land is frequently ploughed and cropped 

 and wot properly manured. To keep up the supply of organic 

 matter in the soil, see Johnston's Catechism of Agricultural 

 Chemistry. The inorganic or earthy parts of the soil serve two 

 purposes : First, " as a medium in which the roots can fix them- 

 selves so as to keep the plants in an upright position." Second, 

 it supplies the plants with inorganic food. The inorganic. part 

 of the soil consists chiefly of sand, clay and lime ; but contains 

 small quantities of the same substances which exist in the ash 

 or inorganic part of the plants. These substances are dissolved 

 by the rain and spring waters and sucked up by the roots of 



