xiv THE LIFE OF THE PLANT 



FAGS 



absorption of oxygen — respiration. Loss in weight and rise of 

 temperature as a result of respiration. Importance of the 

 surrounding temperature. Temperatures : maxima, minima, and 

 optima. Effect of the age of the seed on its germination. 

 Longevity of seeds. General characteristics of the period of 

 germination. Division of labour between different organs of 

 the plant, already apparent in the lowest plants . 59 



IV 

 THE ROOT 



Function of the root. Composition of the soil. Method for 

 defining the necessary nutrient substances. Artificial cultures. 

 Cultures without organic matter. Water cultures. Importance 

 of nitrogen, potassium, iron, sihcon. The necessary nutrient 

 substances absorbed by the root. Nutrient substances in the 

 soil for immediate use and in reserve. Absorbent properties 

 of the soil. Importance of saltpetre in the soil. Assimilation 

 of nitrogen by leguminous plants. Form in which nutrient 

 substances are found in the soil. 



Structure of the root. Its striking elongation and the 

 purpose of this character. The root in relation to liquid and 

 sohd substances. General mechanism for the absorption of 

 nutrient substances by the root ... .88 



THE LEAF 



Function of the leaf. The nutrient substance assimilated by the 

 leaf. The leaf in relation to carbonic acid. Structure of the 

 leaf. Evolution of oxygen. Decomposition of carbonic acid 

 in water. Obviousness of the experiment. Decomposition of 

 carbonic acid in an artificial mixture of gases and in the 

 atmospheric air. Formation of a carbohydrate (starch) in the 

 chloroplast. 



The decomposition of carbonic acid from the point of view 

 of the transformation of energy. Nutrition of the plant at the 

 expense of organic matter. Fungi and parasites. Physio- 

 logical functions of the leaf . . . . .119 



VI 



THE STEM 



Function of the stem, secondary as a medium between the leaf and 

 the root. Forms of stems. Internal structure. Cell, fibre, 

 and vessel. Three types of tissue : nutritive, mechanical, and 

 conducting. Connective tissue and bundles. Structure of 

 stems in monocotyledonous and dicotyledonous plants. Wood 

 and bark. 



Ascending current of water. Its course and destination. 

 Participation of the root — ^its water-raising power. Participa- 



