USE OF BOTANICAL IS AMES. 
127 
a. 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 micro- 
scope ; but if experience teach us that the characters most constant and proper 
for the explanation of physiological phenomena can only be discovered by such aid, 
it is necessary to resort to this instrument in order to estabhsh the natural rela- 
tions of plants. 
162. It is evident, by the formation of species^ genera^ and 
families^ that every species should offer the essential characters 
of the family and genus to which it belongs ; while the marks 
which distinguish this species from another species of its genus 
will be such as do not belong to the whole genus or family. 
The different genera in families are also distinguished by char- 
acters which do not belong to the whole family ; every indi- 
vidual, then, will possess its specific character, its generic char- 
acter, and its family character. The specific character is less 
important than the generic, as it is mostly founded on the char- 
acters of the organs of vegetation^ which are isolated^ and less 
important than the coexistent characters. We often find, in 
the analysis of plants, a great difficulty in determining their 
species, from the want of definite marks of distinction. Gener- 
ic cha/racters are mostly of the coexistent kind, and are more 
valuable than the specific characters. The distinctions of 
genera are usually much more apparent than those of species ; 
as a rose can be more easily distinguished from a Rubus, than 
one species of rose from another species. Families are grouped 
together by marks of resemblance found in genera. These 
family characters are, of all others, the most important. In the 
artificial classes and orders we depend on what we have before 
i^Tm^^ factitious characters. In species, genera, and families, 
the essential characters are also natural cha/racters. 
LECTUEE XXIY. 
USE OF BOTANICAL NAMES. ARTIFICIAL CLASSES AND ORDERS CON- 
SIDERED IN GROUPS. CLASSES MONANDRIA AND DIANDRIA. 
163. "We will examine each class of the Linngean system 
separately, with the orders it contains, and notice some of the 
most remarkable plants and natural families with which we 
shall meet in our progress. This system appears to be the best 
method yet discovered of classing new plants, and of ascertain- 
ing the botanical names of those which are already known. 
If in all countries the common names of plants were alike, 
there would be no need of any other ; but the names of plants 
a. In what cases should we make use of characters invisible to the naked eye 1 — 162. Characteristic* 
»f species, genera, and natural families. — 163. Common names variable. 
