BIOLOGY OF PLANTS 



CHAPTER L 



THE VITAL PRINCIPLE. 



Material bodies have been divided into three kingdoms, 

 animal, vegetable and mineral. This division is an obvious 

 one, and is a convenient mode of classifying the phenomena 

 which each presents to the view of the common observer. 



But a more philosophical examination discloses the fact, 

 that animals and vegetables have many points of analogy, and 

 that they both differ essentially, from minerals. This differ- 

 ence is manifested in various ways, in the mode of their origin, 

 their food, growth and dependance upon other matter, foreign 

 to themselves. But all these different modes of existence 

 may be traced to a peculiar power, which has been called the 

 vital principle ; hence a more philosophical division of natural 

 objects, is into those which arepossessed of life, and those which 

 are destitute of it. The former have been called organic, 

 and the latter inorganic bodies. 



Sect. 1. Defnitions. — Proofs, Nature and Uses of the Vital 

 Principle. 



1. Biology is the science of life. The term is derived from 

 two Greek words, and is similar in signification to the term 

 Physiology. It includes all the agencies and conditions which 

 are essential to the existence and reproduction of living beings. 

 The term Biology of plants signifies nearly the same as vegeta- 

 ble physiology. It includes that peculiar power which has been 

 called the " vital principle,''^ and its connection with those agen- 

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