Vlll PREFACE. 



of as a check upon the first. At last some one will 

 tell him that his plant is a Polygonum; he turns to 

 his hook, wondering how he could have overlooked 

 it ; and he finds Polygonum in Octandria. Should 

 he inquire how this is, he will learn that his species 

 belongs to Octandria, not because it is octandrous, 

 but because it is so very like other Polygonums that it 

 cannot be separated from them, and they belong in most 

 cases to Octandria. This is the unavoidable answer ; 

 and what does it really mean, except that it is not in 

 consequence of its accordance with the system that 

 the student's Polygonum is to be discovered, but in 

 consequence of its natural relation to other Polygonums; 

 so that it is necessary to understand the Natural 

 System, to make use of the Artificial System ! This is 

 no exaggerated case, but one of common occurrence. 

 It is undoubtedly true that in some books such incon- 

 venience is guarded against by special contrivances ; 

 but those contrivances form no part of the system. 



Granting, however, for argument's sake, that these 

 and other objections are overstated, and that the 

 Linnean system does really facilitate the discovery of 

 the class and order to which a plant belongs, let us 

 next consider what advance towards the determina- 

 tion of the genus and species, or in other words the 

 name of a plant, a student has really made, when the 



