USE OF BOTANICAL HAMES. 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 tlie 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 establish the natural rela- 

 tions of plants. 



162. It is evident, by the formation of spedes^ 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 sjKcific 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 cha/r- 

 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 characters 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 i?ose 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 

 tQYm.Qd factitious characters. In species, genera, and families, 

 the essential characters are also natural characters. 



LECTURE XXIY. 



USE OF BOTANICAL NAMES. AKTIFICIAL CLASSES AND OEDERS CON- 

 SIDERED IN GROUPS. CLASSED MONANDRIA AND DIANDRIA. 



163. We will examine each class of the Linnsean 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 hotanical namss of those which are already known. 

 If in all countries the common names of plants wero alike, 

 there would be no need of any other ; but the names of plants 



a. In what cases should we make nse of characters invisible to the naked 83-6 ?— 1G2. Characteristics 

 If species, genera, and natural families.— 163. Common names variable. 



