220 BOTANICAL CLASSIFICATION AND ANALYSIS 



A species is considered as an nitimate individual kind of plant, like 

 the Red Maple, the ordinary medicinal Wild Cherry, or the Two-leaved 

 Pink Ladyslipper. 



Varieties. — Varieties frequently exist among the individuals of a 

 species. It is practically impossible to establish rules for determining 

 whether two closely related forms are two species or two varieties of 

 one species, and there is hardly a point upon which our botanists are 

 more at a disagreement than in estimating these cases. It may be said 

 that a variety is a form of a species which depends either upon a natural 

 tendency to vary, or upon modifications brought about by difl'erent 

 climatic conditions or other environment, but which, in either case, is 

 not permanently fixed, its descendants being liable under various con- 

 ditions to reassume the characters of the parent. The characters of a 

 species are, upon the other hand, supposed to have become permanently 

 fixed. It may, of course, vary, but there is no special tendency for it 

 to vary in the direction of the ancestral form more than from it, in a 

 new direction. 



Forms. — Variations which are not at all fixed, and clearly temporary 

 in their nature, as the occurrence of a white fiower among plants habitu- 

 ally blue-flowered, give rise to Forms. These are hardly considered 

 worthy of names. 



Botanical Analysis. — This consists in the determination of the botani- 

 cal ])osition and name, if it have one, of a plant, by comparing it with 

 published descriptions until that one is found with which it agrees. 

 To make such comparisons individually, and without system, would 

 prove interminable among such a vast number of species, and the system 

 of classification above mentioned is employed to reduce to a minimum 

 the time and labor required. The process is essentially one of successive 

 exclusions of the plant under study from more or less extensive divisions 

 and subdivisions. 



By determining that our plant produces flowers and seeds, we exclude 

 it from the Cryptogamia, approximately half of the vegetable kingdom. 

 Another similar act excludes either the Angiospermae or Gymnospermae 

 and another, if it be an Angiosperm, from either the Monocotyledones 

 or Dicotyledones. As the process continues, it becomes somewhat more 

 complicated. The first steps may be positively taken by deciding a 

 single point, but farther on, in determining the family, genus, and 

 species, groups of characters have to be considered together, and 

 held in mind at the same time for comparison. This is in general due 

 to the fact that the characters separating the primary groups are 



