Xixii INTRODUCTION. 



While, however, the impracticability of absolute definitions is thus 

 insisted upon, there can be no doubt that mucb more precision maybe 

 introduced than is too frequently found among them. Exceptions, although 

 to -"in" extent inevitable, are not uncommonly apparent, not real. It will 

 frequently be found that a particular species is at variance with the defini- 

 tion of ita Genus, or of a Genus with that of its Order, or of an Order with 

 thai of ita Alliance ; but, upon a full examination of all the structure of such 

 supposed exceptions, it will turn out that they are misplaced, and do not in 

 fad belong to the Btation which they occupy. Exceptions of this kind were 

 former!} *-ery common, but they are disappearing under the diligent cri- 

 tichun of modern observers. The genus Rhynchotheca may be taken as an 

 example. The great feature of the Cranesbills is their beaked torus and 

 folded-up embryo, and it ia by that circumstance that they are essentially 

 distinguished from their neighbours. But Rhynchotheca was described as 

 having a beaked fruit and straight embryo ; it therefore formed an apparent 

 exception to the definition of Cranesbills. Investigation of the plant has 

 however shown that its beak belongs to the carpels and not to the torus ; and, 

 therefore, it is merely an Oxalid, with a tendency towards the structure 

 of a Cranesbill. 



The manner in which the foregoing principles have been applied to prac- 

 tice has differed greatly, and the result has been schemes of various degrees 

 of merit, some of which have dropped still-born from the press, while others 

 continue to enjoy a well-deserved reputation. It would be alike unjust to 

 their authors and the public to omit all mention of even the most obscure 

 of these, each of whieh has been the result of much thought and patient 

 Btudy, and has doubtless contributed something to the progress of system- 

 atic -rienee. Bui it would be beyond the object of the present sketch to 

 treat them all at length, nor would the student derive any advantage from 

 doing bo. While, therefore, the following pages will be occupied by some 

 account of every plan for a Natural classification of which I have any know- 

 •,* >ince the year 17< s '.l inclusive, and of those of Ray and Linuams of 

 an earlier date, such as are comparatively unimportant will be dismissed in 

 a few words, and those only which have been really employed in practice 

 will be Btated at Length. In order to render the latter more useful, references 

 are given t" the pages in the present work where an account of each Order 

 in av be found : so that those who are accustomed to the use of other sys- 

 tema may nol experience inconvenience from the arrangement proposed in 

 the work now submitted to their consideration. 



• i do not, however, Include the arrangements of the German NaturphfloBopbists ; not, indeed, 

 from any dltreeped t<> those learned nun. but because 1 must confess my inability to master their ideas, 

 iTtn comprehend how thnr views are made applicable to any intelligible classification. The student will, 

 t believe, Bud full information upon the subject IsOken's Lehrbuch der Naturphilosophie, edition of 

 IM.'l - i Retehenbach'l i RegvA Vegttabilil, 1828, the same author's Flora Oerma- 



iiiV.i Exeurtor and Bchults Fat • yittm dei Pjkmsenrtichs, \W2. 



