14 INTRODUCTION. 
Linnzan system, when applied with the aid of books, possesses facilities 
which are (at present at least) greatly superior to those afforded by the 
other, and which are well calculated to encourage a learner. To count 
the number of stamens and pistils is generally a very easy process ; this 
at once establishes the class and order; and nothing then remains 
but to determine the genus and species, which (among the number 
found in the Northern United States) a little practice in the examination 
of characters will enable any intelligent person to do with the 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 Linnzan 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 Monocoty- 
ledon,) since under the same head are grouped genera of the most 
opposite character. It may be said that it serves 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 interes of the general scope of the book, nor of the mode in which 
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IMPERFECTIONS OF THE LINNEAN SYSTEM. 
9. The Linnzan system is liable to many imperfections and difficulties 
in its application, even in the limited circle of the plants of the United 
States ; for example, the number of pistils is liable to be altered in any 
species by the more or less complete adhesion of the carpels; and 
that of the stamens may also vary in the different species of the same 
genus, and even among the individuals 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 confusion. For instance, of the genus Polygonum, 
of which several species are known by the name of Bistort, Buckwheat, 
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 number, 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 student meet with a specimen which has five, six, or 
ten stamens, he will vainly search for its character among the genera of 
the Linnean class to which it would seem to belong: and unless he 
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