PREFACE. 



THE first edition of Gray's Manual was published in 1848. 

 It was to a great extent rewritten and its range extended in 

 1856, and it was again largely rewritten in 1867. The great 

 advances that have since been made in systematic botany and 

 in the knowledge of our flora have for several years past made 

 another revision desirable, which Dr. Gray before his death 

 was purposing to undertake. 



The present editors, acting to the best of their ability in 

 his stead, have endeavored throughout to follow his methods 

 and views. The original plan, so long retained by Dr. Gray 

 and so generally approved, has been closely adhered to, the 

 characters and descriptions of the last edition have been left 

 essentially unchanged so far as possible, and in the numerous 

 alterations and additions that have been considered necessary 

 or advisable, his conclusions and principles have governed in 

 every matter of importance, so far as they could be known. 

 The effort especially has been to maintain that high standard 

 of excellence which has always made the Manual an authority 

 among botanists. 



In the treatment of the genera and species, Gray's Synoptical 

 Flora has been made the basis in the revision of the Gamopet- 

 alous Orders, and his manuscript in continuation of that work, 

 so far as prepared, for the Polypetalous Orders which precede 

 Leguminosce (excepting Nupliar, the Cruciferce, Caryopliyllacecp^ 

 Vitis, and the small Orders numbered 18, 22, 23, 25-27, and 

 29). The genus Salix has been rewritten for this edition by 

 M. S. BEBB, Esq., the genus Carex by Prof. L. H. BAILEY, and 

 the Ferns and allied orders by Prof. D. C. EATON. For the 

 rest, all known available sources of information have been 

 made use of, and much willing help has been received from 

 botanists in all parts of our territory. 



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