SECTION 18.] TERMINOLOGY. 181 



543. So a plant is named in two words, the generic and the specific 

 names, to which may be added a third, that of the variety, upon occasion. 

 The generic name is peculiar : obviously it must not be used twice over in 

 botany. The specific name must not be used twice over in the same genus, 

 but is free for any other genus. A Quercua alba, or White Oak, is no 

 hindrance to Betti/a alba, or White Birch ; and so of other names. 



541. Characters and Descriptions. Plants are characterized by a 

 terse statement, in botanical terms, of their peculiarities or distinguishing 

 marks. The character of the order should include nothing which is com- 

 mon to the whole class it belongs to ; that of the genus, nothing which is 

 common to the order; that of the species nothing which is shared with 

 all other species of the genus; and so of other divisions. Descriptions 

 may enter into complete details of the whole structure. 



545. Terminology, also called Glossology, is nomenclature applied to 

 organs or parts, and their forms or modifications. Each organ or special 

 part has a substantive name of its own : shapes and other modifications of 

 an organ or part are designated by adjective terms, or, when the forms 

 are peculiar, substantive names are given to them. By the correct use 

 of such botanical terms, and by proper subordination of the characters 

 under the order, genus, species, etc., plants may be described and deter- 

 mined with much precision. The classical language of botany is Latin. 

 W r hile modern languages have their own names and terms, these usually 

 lack the precision of the Latin or Latinized botanical terminology. For- 

 tunately, this Latinized terminology has been largely adopted and incor- 

 porated into the English technical language of botany, thus securing pre- 

 cision. And these terms are largely the basis of specific names of plants. 



546. A glossary or vocabulary of the principal botanical terms used in 

 phanerogamous and vascular cryptogamous botany is appended to this 

 volume, to which the student may refer, as occasion arises. 



3. SYSTEM. 



547. Two systems of classification used to be recognized in botany, the 

 artificial and the natural ; but only the latter is now thought to deserve 

 the name of a system. 



548. Artificial classifications have for object merely the ascertaining 

 of the name and place of a plant. They do not attempt to express relation- 

 ships, but serve as a kind of dictionary. They distribute the genera and 

 species according to some one peculiarity or set of peculiarities (just as a 

 dictionary distributes words according to their first letters), disregarding 

 all other considerations. At present an artificial classification in botany 

 is needed only as a key to the natural orders, as an aid in referring an 

 unknown plant to its proper family ; and such keys are still very needful, 

 at least for the beginner. Formerly, when the orders themselves were 

 not clearly made out, an artificial classification was required to lead the 



