C&AKACTEKS USED IN CLASSIFICATION. 
125 
.ongs, and thus learn its habits, medicinal use, and other important particular!. 
The natural method may be considered as the grammar of botany ; for between 
this and the artificial system the same relation exists as between the grammar 
and dictionary of a language : it would be idle to attempt to decide on theii com- 
parative merits, since both are essential to science. 
158. Rules for classification. ^ — All hotanical classification re- 
sults from an EXAMINATION and comparison of plants. 
Every oi'ganic distinction which establishes between individu- 
als any resemblance, or any difference, is a cha/racter / that 
is, a sign by which they may be Icnown and distinguished. 
The presence of an organ.^ its different modification, and its 
absence, are so many characters. 
The presence of an organ furnishes positive characters — its 
ABSENCE, NEGATIVE CHARACTERS. 
159. Positive characters offering means of comparison, show 
the resemblances and differences which exist between indi- 
viduals ; those plants in which these characters present but 
slight differences, should be collected in groups ; those in 
which these characters differ more sensibly, should be sep- 
arated : here we follow strictly the laws of the mind. But 
negative characters, as they allow no comparison, can only be 
employed to separate individuals, and never to bring them 
together. When we say i\i2X plants han^e seeds with one or two 
cotyledons / that they have monopetalous or polypetalous fiow- 
ers, and are provided with stamens and pistils, we point out 
particulars where visible and striking resemblances may be ob- 
served j these cha/racters, then, o/re positive, since they are 
founded on something real. 
When we say that some plants are destitute of cotyledon, 
corolla, stamens, or pistils, we do not establish any real basis 
for the foundation of a comparison. If we wish to separate 
plants with monopetalous corollas from such as have polypet- 
alous corollas, this single cha/racter establishes, at once, the 
difference which exists between the two groups, and the resem- 
blam.ce which exists between individuals of each group. Thus, 
positive characters possess a great advantage over negative ones / 
the latter should never be employed when the former can be 
used ; and in proportion as positive characters can be substi- 
tuted for negative, the science of botany will be perfected. 
Positive characters can only be founded upon evident facts, 
and never upon ?i. presumption of the existence of facts, derived 
from analogy ; for it is contrary to true philosophy to suffer 
hypothetical reasoning to usurp the place of direct observation 
• These rules are chiefly translated from Mirbel's " Elemens de Botanique." 
The natural method considered as the grammar of botany. — 158. Rules for classification, — 159. Posi 
tive and negative characters — Advantage of positive characters over negative — Positiire character* 
foun led only upon evident facts. 
