PREFACE. 



have only for a short time occupied the atten- 

 tion of observers, or which depend upon obscure and 

 iU-understood evidence, are by no means so clearly 

 defined as could be wished. To explain those prin- 

 ciples, to adduce the evidence by which their truth 

 is supposed to be proved, or the reasoning upon 

 which they are based in cases where direct proof is 

 unattainable ; to show the causes of errors that are 

 now exploded, and the insufficiency of the arguments 

 by which doubtful theories are still defended, — in 

 fine, to draw a distinct line between what is certain 

 and what is doubtful, — are some of the objects of this 

 publication, which is intended for the use of those 

 who, without being willing to occupy themselves 

 with a detailed examination of the vast mass of evi- 

 dence upon which the modern science of botany is 

 founded, are, nevertheless, anxious to acquire a dis- 

 tinct idea of the nature of that evidence. Another 

 and not less important purpose has been to demon- 

 strate, by a series of well-connected proofs, that in no 

 department of natural history are the simplicity and 

 harmony that pervade the universe more strikingly 

 manifest than in the vegetable kingdom, where the 

 most varied forms are produced by the combination 

 of a very small number of distinct organs, and the 

 most important phenomena are distinctly explained 

 by a few simple laws of life and structure. 



In the execution of these objects, I have followed 

 very nearly the method recommended by the cele- 

 brated Professor De CandoUe, than whom no man is 

 entitled to more deference, whether you consider the 

 soundness of his judgment in all that relates to order 

 and arrangement, or the great experience which a 

 lono- and most successful career of public instruction 

 has necessarily given him. 



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