PREFACE TO THE FIRST EDITION 



After more than twenty-five years of study of the flora of the Rockj' Mountain 

 region, and seventeen j^ears after the first description was drawn for the book, 

 this manual is now presented to the public. Its history, purpose and scope are 

 given in the introduction, with certain necessary explanations regarding the 

 general features of the book. 



Thanks are due to the custodians of many herbaria for the privilege of study- 

 ing collections and types, and for the loan of specimens; these herbaria are 

 envmierated in my introduction. The author wishes to thank all his associates 

 at the New York Botanical Garden, especially Dr. N. L. Britton, Director-in- 

 Chief, for encouragement and help in his work; Dr. J. K. Small, for help in critical 

 cases and in certain groups, as for instance PoLYGO^AKbEAE and Saxifragaceae, 

 and in the original draft of the key to the families; and Dr. J. H. Barnhart, for 

 help in questions of nomenclature and literature. In drawing the generic des- 

 criptions, the author has frequently consulted Dr. Small's Flora of the Sotjth- 

 easterx United States. Dr. Barnhart has contributed also the list of authors, 

 including their full names and years of births and deaths wherever it has been 

 Ijos.sible. 



Thanks are also due to Mr. K. K. Mackenzie, who contributed the manu- 

 script of Carex; to Professor E. Brainerd, who prepared that of Viola; and to 

 ]\Ir. W. W. Eggleston, who revised that of Crataegus. 



As most manuals of phaenerogamic botany also contain the ferns and their 

 allies, an account of the fern-worts by Miss Margaret Slosson has been apjiended. 

 The families Isoetaceae, Eqxjisetaceae and Selaginellaceae were left by 

 her until the last. She did some preliminary work on Selaginella, but before the 

 work was finished she left the New York Botanical Garden temporarity, and 

 the completion of the fernworts fell upon the author, who feels that the treat- 

 ment of the three families is not adequate, as the manuscript was prepared hur- 

 riedly while the book was going through the press. 



The author is indebted especially to the following botanists, who have kindly 

 corrected the statements of the ranges of all the species and furnished additions 

 to the list of species known to occur in their respective states and provinces: 

 Mr. J. M. Macoun, western Canadian provinces; Professor J. E. Kirkwood, 

 Montana; Mr. J. Francis IMacbride, Idaho; Professor A. O. Garrett, Utah; 

 and Mr. George E. Osterhout, Colorado. Thanks are also due to the following 

 persons who have gratuitously helped in reading the proofs: Professor A. O. 

 Garrett, Mr. G. E. Osterhout, Miss K. D. Ivimball. 



P. A. Rydberg. 

 The New York Botanical Garden, November, 1917. 



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