PREFACK. 



The outline of this work was presented as a communication to the 

 Philosophical Society of Washington, January 22, 1881. The aim of 

 the writer was to furnish a guide to botanists in exploring the locality 

 and an aid to beginners in practical botany. To this latter class the 

 Appendix is especially addressed, but as it is equally applicable toother 

 localities, and as nothing, it is believed, analogous to it has been pub- 

 lished, it may be found useful outside of Washington. The introduction 

 also contains suggestions which, if followed in a sufficient number of 

 localities by those pieparing local catalogues, would greatly aid in 

 making the botanists of the country acquainted with the geographical 

 distribution of plants thoughout the United States and the special peculi- 

 arities of certain regions. 



Tlie manifest imperfections of the treatise may not be without their 

 uses in stimulating local collectors and others to correct them and pro- 

 duce something better. 



In the investigation of the flora of Washington, so many able and 

 active botanists and so many energetic amateurs have co-operated that 

 it would almost seem invidious to single out any as the subjects of 

 special thanks, and it has been deemed the most equitable plan to give 

 ^special credit to the first discoverer of each rare jjlant, wherever this can 

 be known, under its proper head in the detailed enumeration. I cannot, 

 however, refrain from expressing my special obligations to Dr. George 

 Yasey, Botanist to the Department of Agriculture, for his kindness in 

 placing the National Herbarium at my disposal and in examining and 

 reporting upon many critical and puzzling forms, especially in the 

 OyperacesB and Graminese. I also desire to acknowledge in an especial 

 manner the valuable services of Mr. M. S. Bebb, of Eockford, 111., in 

 identifying the local Salices, which, though comparatively few, are very 

 interesting and in a high degree confusing to any but a trained specialist 



like Mr. Bebb. 



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