CONTENTS XV 



Page 



40. Chlorophyll Formation. Etiolation and Chlorosis 173 



41. Absorption of Light Energy by Chlorophyll 175 



42. Quantitative Relations between Absorbed and Stored Energy 

 in the Plant. Decomposition of Carbon Dioxide by Energy 

 Obtained from Oxidation. Chemosynthesis 178 



43. Chemical Reactions of Photosynthesis. Theories of von Baeyer, 

 Willstatter, and Warburg 184 



44. Structure of the Leaf as an Organ of Photosynthesis. Penetration 



of Carbon Dioxide into the Leaf 188 



45. Dependence of Photosynthesis on Light Intensity. Sun and Shade 

 Plants. Culture of Plants in Artificial Light 193 



46. Dependence of Photosynthesis on the Amount of Carbon Dioxide. 

 The Carbon Dioxide Cycle in Nature 201 



47. Dependence of Photosynthesis on Temperature. The Interaction 

 of Factors and the Law of Limiting Factors. Diurnal Changes 



of Photosynthesis 203 



48. Intensity of Photosynthesis and Yield of Dry Matter. Signifi- 

 cance of the Relation between Photosynthesis and Respiration. . . 210 



49. General Course of the Accumulation of Organic Substance by the 

 Plant during Its Vegetation 214 



CHAPTER VI 

 Assimilation of Nitrogen by Plants 



50. Absorption of Nitrogen from the Soil. Nitrates and Ammonium 

 Salts as Sources of Nitrogen 219 



51. The Products of Nitrogen Assimilation and Its Connection with 

 Photosynthesis. Primary Synthesis of Protein Substances 224 



52. Assimilation of Molecular Nitrogen of the Atmosphere by Soil 

 Bacteria 228 



53. Assimilation of Molecular Nitrogen by Symbiotic Bacteria and 

 Leguminous Plants 231 



54. The Nitrogen Cycle in Nature. Artificial Nitrogen Fertilizers . . . 235 



CHAPTER VII 

 Absorption of Mineral Elements by Plants 



55. Mineral or Ash Constituents of the Plant, Their Composition 

 and Origin. Indispensable and Supplementary Mineral Elements 239 



56. Sulphur and Phosphorus, Their Metabolism in Plants and Their 

 Cycles in Nature 245 



57. General Role of Cations and Their Specific Activity 247 



58. Absorption of Mineral Elements by Roots 250 



59. Mineral Nutrition of Plants Grown in Soil 252 



60. Methods of Determining the Nutritive Value of Soils 258 



61. Use of Mineral Elements by Different Plants. The Accumula- 

 tion of Mineral Elements by Plants at Different Stages of Growth. 

 Relation of Plants to Calcium Salts in the Soil 264 



62. Effect on Plants of the Hydrogen-ion Concentration of the Soil . 268 



63. Physiological Basis of Fertilization 273 



