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, 101. 



CHAPTER III 



Carbon and Nitrogen 



i. 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, 1 1 8 ; 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, 126; light as a source of energy, 129; light 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; (b) in perennials, 162 ; (c) in 

 trees, 163 ; (d) in foliage 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, 177 ; nutritive value of different sources of carbon, 



178; omnivors and specialists, 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. 



