DESCRIPTION. 361 



742. Absence of an organ or quality may be expressed by 

 means of a prefix with privative signification, as indehiscent, not 

 dehiscent, exannulate, destitute of a ring, apetalous, without 

 petals. But the Greek privative a should not be prefixed to 

 Latin words, nor the Latin sub to terms taken from the Greek. 



743. When the Latin preposition ob is prefixed to an adjective 

 term, it means obversely ; thus obcordatus is cordate inversed, 

 that is, the broader end with its notch at the apex (instead of 

 the base) of the leaf or other plane organ. 



SECTION III. DESCRIPTION. 



744. Under this head may be conveniently comprised all that 

 relates to the form of the exposition, in botanical terms, of the 

 differences by which the species and groups of plants are distin- 

 guished and recorded, the structure exemplified, and the history 

 or bibliography indicated in systematic works or writings. Lin- 

 naeus, in the Philosophia Botanica, treated these topics under 

 the head of " Adumbrationes." 



745. Descriptions may be full and general, comprising an 

 account of all that is known of the structure and conformation 

 of a plant or group, or rather all that is deemed worth recording, 

 or they may be restricted to what is thought most important. In 

 the former, the description is independent of all relative knowl- 

 edge, or takes no notice of relationship to other plants or groups. 

 The latter intends to portray the species or group in its relations 

 to others, and to indicate the differences solely. Exhaustive 

 descriptions of the former kind are seldom drawn up, but partial 

 or supplementary ones are common. Descriptions of the latter 

 kind, when reduced to what is essential or differential, are termed 

 Characters, or the Character, of the group so described. There 

 are all gradations in practice between characters and descrip- 

 tions ; but the distinction should be maintained. 



746. Characters are specific, generic, ordinal, &c. They are 

 the differentiae, or marks which distinguish a group from any 

 related group of the same rank with which it may properly be 

 compared. According to the occasion and purpose, they may 

 specify only the fewest particulars which will serve as a diag- 

 nosis, or they may be extended to all the known constant differ- 

 ences between two or more related species, genera, orders, &C. 1 



1 The former would answer to what have been termed differential char- 

 acters, the latter to essential characters. Linnaeus divided ( generic ) characters 

 into factitious, essential, and natural; by the former denoting any difference 

 which may effectively distinguish between any two groups brought arti- 



