PLANT LIFE AND EVOLUTION 



CHAPTER I 

 INTRODUCTION 



SPECULATIONS concerning the origin of life 

 upon the earth, and the nature of the primeval 

 organisms from which are descended existing plants 

 and animals must always have for the biologist an 

 irresistible attraction. When we realize the ex- 

 traordinary development of modern experimental 

 biology, it would be rash to say that the problem 

 of the origin of life is insoluble, but it must be 

 admitted that its solution does not seem to lie in 

 the immediate future. 



Life and Its Origin. All living things are built 

 up of chemical elements that also occur in an " in- 

 organic " condition ; and the nature of the combina- 

 tions of these elements into the substances that 

 make up living matter, and the functions or " life 

 processes " associated with this living matter, are 

 the problems with which the biologist has to deal. 

 Whether all of these " vital " phenomena are re- 

 ducible to terms of physics and chemistry, may per- 

 haps be open to question; but as yet we have no 

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