14 ? Principles of Classification-* 
Of Genera and Species. 
Genera.—— The orders are again subdivided into gene* 
i*a. The chai*acteristic marks of the genera are derived 
from the flowers and fruit, and a genus comprehends 
one or more species, which resemble each other in some 
parts of the flower or fruit, or of both. Three kinds 
of generic characters are mentioned by Linnaeus, the 
factitious, essential, and the natural, all depending on 
the fructification alone, and not on the inflorescence or 
on any other part : by the factitious character, genera 
that come together in the same artificial order, or sec- 
tion, are discriminated ; by the essential character, a 
particular genus is distinguished by one striking mark 
from all genera of the same natural order, and, conse- 
quently, from all other plants ; and the natural charac- 
ters include all the marks common to all the species of 
the genus. The natural character of genera is employ- 
ed by Linnaeus in his Genera Plafitarum ; but to this 
-method of discrimination it has been objected that it 
does not direct the mind to the most important marks, 
and that it only accords with such species of the genus 
►as are known to the author, from which, it is obviously 
imperfect ; but the essential character, which is now 
universally adopted to distinguish genera, comprehends 
all the marks necessary to discriminate each genus from 
every other in -the system. 
Species . — The Characters which are employed in dis- 
tinguishing species should be constructed on the same 
principles as the characters of the genera, and they 
ought to be certain, clear and concise# No characters 
