USE OF THE LINN.fi AN SYSTEM. 319 



process ; this at once establishes the class and order ; and nothing 

 then remains, but to determine the genus and species, which 

 (among the comparatively small number found in Britain) a little 

 practice in the examination of characters will enable any intel- 

 ligent person to do, with tlie aid of books in which these are laid 

 down. The habit thus gained of discriminating characters, and 

 of applying terms, is a most valuable preparation for the study 

 of the Natural System when opportunity presents itself. It must 

 be constantly borne in mind, however, that the utmost use which 

 can be made of the Linnsean system, consists in the assistance it 

 affords in the discovery of the name of an unknown plant ; and, 

 until this has been made out, the previous determination of its 

 class and order gives no indication of its general structure and 

 properties (not even making it apparent whether it is an Endogen 

 or an Exogen, a Dicotyledon or a Monocotyledon), since under 

 the same head are grouped genera of the most opposite character. 

 It may be said that it serves as a sort of Alphabetical index to a 

 book, enabling the reader to turn to any part of it he wishes, by 

 looking out the subject in the order of its first letters, but giving 

 no idea whatever of the general scope of the book, nor of the 

 mode in which its subjects are arranged. 



481 . The Linnaean System is liable to many imperfections and 

 difficulties in its application, even in the limited circle of British 

 Plants ; for example, the number of pistils is liable to be altered 

 in any species by the more or less complete adhesion of the car- 

 pels; and that of the stamens may also vary in the different 

 species of the same genus, and even among the different indivi- 

 duals of the same species, or even (in some instances) among the 

 different flowers of the same stem. The adoption of characters 

 thus liable to vary cannot, therefore, but sometimes lead to con- 

 fusion. For instance, of the genus Polygonum, of which the 

 several British species are known by the names of Bistort, Buck- 

 wheat, Persicaria, &c., one has always, and two others have 

 occasionally, eight stamens ; whilst in the rest the number varies 

 from five to ten. As eight seems to be the most regular num- 

 ber, the genus is placed in the class Octandria : and although its 

 styles are sometimes only two in number, it is placed in the order 

 Trigynia, because they are more commonly triple. Now if a 



