xvi THE LIFE OF THE PLANT 



PAGE 



and amaesthesis in plants and animals. Is a plant capable of 

 consciousness ? The difference between plants and animals 

 is not that of quality but otquantity — not in kind, but in degree. 

 The sum-total of experimental physiology does not exhaust the 

 problems of the science . . . .252 



X 



ORIGIN OF ORGANIC FORMS 



The adaptive character of organic forms can be explained only by 

 the historical process of their development. Palaeontology, 

 morphology, and embryology together testify to the genetic 

 connexion between organisms. This conclusion conflicts with 

 the once prevalent conviction as to the permanency of species. 

 Are species really invariable ? Logical fallacy underlying this 

 opinion. 



Why does the historical process lead to perfection ? Darwin's 

 theory. The struggle for existence and natural selection. 

 Explanation of the absence of transitional forms. What we 

 have to be content with in explaining particular cases of 

 adaptation. Analytical and synthetical paths followed by 

 the reader. General conclusion and aim of the course . 289 



APPENDIX 



THE PLANT AS A SOURCE OF ENERGY 



Twofold significance of food for the animal organism — as a building 

 material and as a source of energy. Conception of work and 

 energy, actual and potential. Law of the conservation of 

 energy. Mechanical theory of heat. Chemical affinity. The 

 animal organism, considered as a mechanism. Combustion 

 and respiration. 



Necessity for the existence in nature of a process the inverse 

 of combustion and respiration. Priestley's discovery. Decom- 

 position of carbonic acid by the plant. This process considered 

 from the point of view of the theory of the conservation of 

 energy. Robert Mayer. Production of organic matter by the 

 plant. Chlorophyll, its optical properties, and the explanation 

 they afford of its function in nature. Economic value of the 

 process taking place in the green organs of plants. Theoretical 

 limit to the productiveness of the earth General inference . 324 



