INTRODUCTION. 21 



independent work, than references in all cases to the 

 original sources of information. Less accessible works 

 have often been cited to introduce the student at 

 once to the most complete treatment of the subject. 

 A few citations are for the sake of authority. 



Many of the memoirs and articles cited in apparently 

 inaccessible foreign journals and proceedings of socie- 

 ties may, however, be bought separately of foreign 

 dealers (R. Friedlander & Sohn, Berlin N. W., Ger- 

 many, and many others). A very moderate outlay 

 will thus enable one to consult numerous valuable 

 writings. 



No apology need be offered for referring in an 

 elementary work to writings in foreign languages, for 

 unless the student carries his researches outside this 

 manual he will have no occasion to use them, and if 

 he does do so he can not go far without being obliged 

 to use them. It is not often possible in fact to treat a 

 subject exhaustively in the departments of botany 

 covered by this handbook without a knowledge of 

 German and French writings at least. 



But if the references given among the annotations 

 are never used, they will still serve a good purpose in 

 impressing upon the learner that he is only upon the 

 threshold of the study, and that the facts which he 

 seems to be gathering so thoroughly are in most cases 

 to be found more fully and accurately set forth in the 

 great storehouse of learning beyond. 



