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PREFACE. 



IX 



in the more extended and very erudite system of 

 the yomiger Jussiou ; and without particularly 

 tracing- the alterations and improvements, from time 

 to time made by the latter author, i n tjie termination 



of the names of his orders, and in the disposition 

 of some of his genern, 1 have endeavoured to keep 



pace 



with 



our 



advancing knowledge by very 



frequent references to recent sources of informa- 

 tion; and herein, more parti cnlarly, to the labours 

 of M. Do CandoUe, and Mr. Robert Brown. Tn 

 these authors most ample details of generic dis- 

 tinctions will be found, to which I think it sufficient 

 to direct the attention of the botanical student. 



That very considerable difficulties ob>struct the 

 formation of a natural arrangenu^nt of plants was 

 perceived and explained by Linmeusj and it is 

 certain, that all attempts hitherto made have been 

 clogged with imperfections and inconsistencies. 

 The plan itself of Jussicu is indeed not entirely 

 natural: the foruuition of Iris classes, from the 

 cotelydons and ilu.) position of the stamens, is beyond 

 doubt artificial; and the classes of Do CandollojOn 

 the same principle, are not proposed by that 



author as natural. 



le distinction of some orders 



is, moreover, entirely dependant on definitions, in 



Many other orders, 



a great degree arbitrary. 



however, are so purely natural, I hat we may rea- 



