48 ELEMENTS OF BOTANY. 



in the knowTi world having the general structure of a gentian, comprising 

 many genera, as gentiana, sabbatia, fraaera, etc. 



The genus gentiana includes all the gentians, and their names are 

 written thus : 



Gentiana quinqueflora Lamarch — Five-flowered gentian. 



Gentiana crinita Froelich — Fringed gentian. 



Gentiana Andrewsii Grisebach — Andrews' gentian, etc. 



The words Lamarck, Froelich, and Grisebach being the names of the 

 botanists who described the plants and gave them their specific names. 



Such is a brief outline of the classification of plants at present em- 

 ployed. It is variously modified to suit circumstances, but these modifi- 

 cations do not require our attention here. There is, however, one point 

 which requires a passing glance. In speaking of species, these were 

 treated of as being absolutely distinctive. Now, in reality this is far from 

 the fact, for often species — as described — are difficult to distinguish one 

 from another. Again, the same species may present plants of, in some re- 

 spects, different aspects ; as for example, a plant whose flowers are habitu- 

 ally blue may joroduce individuals with white flowers. Now Avhen such 

 variations from the specific standard tend to reproduce themselves year 

 after year, they are termed varieties ; hence we not unfrequently see the 

 specific name followed by the word variety and another name, as Anemone 

 patens Linne, var. NuttalUana Gray, signifying that the plant is a variety of 

 anemone patens as characterized by Linne, which variety was named for 

 Nuttall and described by Gray. 



The plants of any region or country arranged systematically according 

 to this — or any other — system of classification is termed the flora of that 

 region or country, and such a flora is of immense service to the student 

 who wishes to familiarize himself with the plants about him. With this 

 flora before him and an unknown plant in his hand, he is enabled to trace 

 out analytically, step by step, the relationship of the unknown with the 

 known, and finally to fix the plant's specific location. 



We Avill suppose him with a flowering jolant in his hand, but one which 

 he has never seen before. He begins by ascertaining whether it be ex- 

 ogenous or endogenous ; if exogenous, whether polypetalous, gamopeta- 

 lous, or apetalous ; and then whether it bear evident relationship to plants* 

 of any order with which he is familiar. If not, he must search through 

 the characters of orders until he can fix its ordinal location, then its ge- 

 neric place, and finally its specific name. For facilitating such analyses arti- 

 ficial keys are supplied in most published floras. 



A medical flora, such as is attempted in the second part of this volume, 

 is an orderly arrangement of the medicinal plants of any region or country. 

 Obviously a key cannot readily be availed of in such a Avork, for, to be of 

 any service, it must be capable of application to all the plants which the 

 territory includes. 



