235 



BOOK II. 



PHYSIOLOGY ; OR, PLANTS CONSIDERED IN A STATE 



OF ACTION. 



GENERAL CONSIDERATIONS. 



We have thus far considered plants as inert bodies, having 

 certain -modifications of structure, and formed upon a plan, 

 the simplicity and uniformity of which is among the most 

 beautiful proofs of the boundless power and skill of the Deity. 



Our next business is to enquire into the nature of their 

 vital actions, and to consider those phenomena in which the 

 analogy that undoubtedly exists between plants and animals 

 is most striking ; in a word, to make ourselves acquainted 

 with the exact nature of the laws of vegetable life. 



In explaining these things, it is not my purpose to notice all 

 the different speculations that ingenious men have from time 

 to time brought forward : for this would be incompatible with 

 the plan of my work, and would be far more curious than 

 useful. On the contrary, I propose, in the first place, to give 

 a summary exposition of the principal phenomena of vegeta- 

 tion, and then to support the statement by a detailed account 

 of the more important proofs of all doubtful points. 



In this I have been most materially assisted by the Physio- 

 logic Vegetale of De CandoUe, a work of wliich it is difficult to 

 speak in terms of sufficient eulogy, but which I feel quite 

 justified in describing as the most important production on 

 the subject of Vegetable Physiology, since the appearance of 

 the Physique des Arbres of Duhamel. 



If we place a seed — that of an apple for instance — in 

 earth at the temperatvu'e of 32*^ Fahr., it will remain inactive 

 till it finally decays. But if it is placed in moist earth above 



