CHARACTERS USED IN CLASSIFICATION. 
133 
when the former can be used ; and in proportion as positive cha- 
racters can be substituted for negative, the science of botany will 
be perfected. 
Positive characters can only be founded upon evident facts^ and 
never upon a 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 of facts. 
5th. Positive characters are constant or inconstant. All seeds pro- 
duced by plants of the same species have the same structure ; all 
plants which grow from these seeds produce other seeds, similar to 
those from which they have had their origin ; of course the charac- 
ters derived from the structure of these seeds are constant. But 
among these plants some are large and others small ; some may 
have white corollas, some red, or blue ; some are more fragrant than 
others ; of course, size, colour, and odour, offer inconstant characters. 
6th. All real science in Botany must rest upon constant characters ; 
therefore, these characters are much more important than the others. 
7th. Constant characters may he isolated or coe.xistent. The petals 
of the RANUNCULUS acris, (butter-cup,) have a nectary in the form of 
a scale ; this character, although constant, is isolated, for it is not 
necessarily connected with any other characteristic trait. The calyx 
of the campanula rotundifolia, (blue-bell,) adheres to the germ ; the 
germ must of necessity -be simple, or without divisions, and the co- 
rolla and stamens attached to the interior of the calyx. The cha- 
racter of the adherence of the calyx to the germ, brings in its train 
several other characteristics ; it is then coexistent ; and is more im- 
portant than the isolated character. 
8th. T'voo orders of characters are derived from the two great divi- 
sions of vegetable organs ; those of vegetation and reproduction. The 
characters of reproduction are 7iumerous and often coexistent ; one 
character serving as an index to many others. 
It is seldom that plants which resemble each other in their charac- 
ters of reproduction, differ much in their characters of vegetation. 
For example ; all plants which have four didynamous^ stamens, at- 
tached to a monopetalous, labiate corolla, and four seeds lying un- 
covered in a monophyllous calyx, have an angular stem and opposite 
leaves. On the contrary, it frequently happens that plants which re- 
semble each other by the characters of vegetation, differ by those 
of reproduction. Labiate and caryophyilous plants agree in having 
their leaves opposite, and yet there is no resemblance in their flow- 
ers. This consideration alone, would seem sufficient for establish- 
ing the superior importance of the characters of reproduction over 
those of vegetation. The seed unites in itself the characters both of 
reproduction and vegetation. The embryo is the commencement of 
the new plant, and it offers us the first characters of vegetation ; but 
its situation in the fruit, the number, form, and consistence of its en- 
velope, are characters which belong to fructification. 
In separating or bringing together plants, we should, as far as 
possible, make use of prominent characters which the eye can see 
without the help of the microscope ; but if experience teaches us 
that the characters most constant and proper for the explanation of 
physiological phenomena can only be discovered by such aid, it is 
* That is, two long and two short stamens. 
.Positive characters founded only upon evident facts— What is the fifth rule?— The 
sixth?— The seventh ?— The eighth 7— Characters of reproduction more important 
than those of vegetation— In what cases should we make use of characters invisibla 
to the naked eye ? 
12 
