PREFACB. Vll 



possible. To Dr. Gray is duo, not onlj the thought whicli 

 grew into this book, but also a constant encouragement and 

 patient criticism which have developed aiiytliing of merit it 

 possesses. Mr. Watson has also responded generously to ev- 

 ery demand made upon him : while to Messrs. M. S. Hebb and 

 L. H. Bailey, Jr. is due the relief of some original work, tin* 

 former being our well-known authority in the difficult genus 

 Salix, and the latter an ardent and most successful student of 

 the perplexing genus Carex. At the time of his death, Dr. 

 George Engelmanu had in preparation the gi'oups with which 

 his name is so closely connected, and their presentation shows 

 the lack of his master hand. 



In general, the ordinal sequence adopted by Bentham and 

 Hooker*s Genera Plantarum has been followed, but G}'!!) no- 

 sperms have been transferred to the end of Phtenogams, 

 and Monocotyledons and Dicotyledons subordinated to Angio- 

 sperms. This change has been made simply because it better 

 expresses relationships which have long been recognized. The 

 term '^ Cryptogam ^' has been discarded as the correlative of 

 Phsenogam, and Pteridophyta (Vascular Cryptogams) is used 

 as the name of the second great series of plants. The orders 

 and ordinal sequence of the Pteridophyta are thought best to 

 express their relationships. 



Introduced plants are placed in foot-notes, that they may be 

 separated as far as possible from our native plants, and their 

 relation to the flora thus empliasized. 



To save space, there is no attempt to give any but the most 

 important references and synonymy, while geographical range 

 is reduced to its lowest terms, and collectors' names ahnost 

 entirely omitted. For the most part no characters liave been 

 repeated, and the student is warned that generic characters 

 especially must be sought for through analytical keys. The 

 professional botanist will note a glaring inconsistency in this 

 respect, the genera of some families being grouped by means 

 of a few very salient characters, while those of others are 

 presented with almost full descriptions, only certain supjdc*- 

 mentary statements being left to head the descrijitions of 



