viii SUMMARY OF CONTENTS 



4. The mineral constituents of the soil. The soil. Origin, 90 ; mineral contents, 



91 ; absorption, 92. The action of the plant on the soil. Union of root- 

 hairs and soil particles, 94 ; excretion of acids, 95 ; renewal of root-hairs, 

 96 ; branching of the root, 97. 



5. Soil and plant distribution. Physico-chemical causes of plant distribution, 97 ; 



association, 99 ; historical causes, 100. 



6. Soil and Agriculture, 10 1. 



CHAPTER III 



Carbon and Nitrogen 



1. Assimilation in Holophytic Plants and Fate of the Products of Assimilation 



a. Assimilation of Carbon. 



1 . The fundamental facts. Proof of the decomposition of carbon-dioxide. Air- 



bubble method, 104; gas-analysis method, 105 ; other methods, 105. Signifi- 

 cance of chlorophyll, 106 ; physical and chemical characters of chlorophyll, 

 107. Concomitant action of sunlight, no. Products of assimilation. 

 Nature, no; amount, 114. 



2. Influence of external factors on carbon-dioxide assimilation. Influence of 



carbon-dioxide. Carbon-dioxide in air, soil, water, 118; influence of con- 

 centration, 119; entry into the plant, 120. Influence of other factors; 

 (i) indirect, through modification of the plant, 121 ; (2) direct influence of 

 oxygen, 124; of temperature, 124 ; of light, 125 ; intensity of light, 125 ; 

 wave-length, 1 26 ; fight as a source of energy, 1 29 ; fight becomes 

 absorbed, 129. 



3. Historical data as to the assimilation of carbon-dioxide, 131. 



b. Assimilation of Nitrogen. Sources of nitrogen, 133 ; gain and loss of nitrogen in 



nature, 135. Absorption of nitrogen, 137. Assimilation of nitrogen. Con- 

 struction of proteid, 138; chemistry of proteid, 138; assimilation of nitric 

 acid, 141 ; of ammonia, 142 ; organic compounds of nitrogen, 143. Assimilation 

 of sulphur and phosphorus, 145. 



c. Fate of the products of assimilation. 



1. Solution of reserves : — {a) in seeds, 148 ; starch, 149 ; diastase, 1 50 ; enzymes, 



152 ; catalytic phenomena, 152 ; action of enzymes on hydrogen peroxide, 

 152 ; incompleteness of the enzyme reaction, 153 ; dissolution of starch 

 in seeds, 154; removal of the embryo, 1 56 ; inhibitory agents, 1 56 ; cellulose, 

 157 ; cell- wall, 157 ; cytase, 158 ; fats, 158 ; chemistry, 158 ; decomposition, 

 159; proteid, 159; pepsin and trypsin, 160; (&) in perennials, 162 ; (c) in 

 trees, 163 ; (d) in fofiage leaves, 164. 



2. Circulation of the dissolved reserves. Migration from the leaf, 166 ; from 



other storehouses of reserves, 167. Causes of the translocation. Diffusion, 

 167 ; accelerating agents, 167. Organs concerned in the transport of material. 

 Parenchyma, 170; sieve-tubes, 170; vessels, 172. Objects of trans- 

 location, 172. 



3. Fate of the translocated materials. Transformation into plasta, 173. Forma- 



tion of reserves. Carbohydrates, 173 ; proteid, 173 ; fat, 175. Formation of 

 waste products, 176. 



2. Acquisition of Carbon and Nitrogen by Heterotrophic Plants 



a. Saprophytes. 



1 . Acquisition of carbon, i yy ; nutritive value of different sources of carbon, 



178; omnivors and speciaUsts, 180. 



2. Acquisition of nitrogen, 181. 



3. Saprophytes in nature, 182; dead organisms, humus, 183; excretion of 



enzymes, 183. 



b. Insectivorous plants, 184. 



c. Parasites, 186, 



d. Metabolism in heterotrophic plants, 188. 



