6 PREFACE 



siderable percentage of plants characteristic of the Great Plains and 

 not harmonious with the flora which the present work is especially 

 designed to treat; and (2) the inchision of the Canadian provinces 

 of Nova Scotia, Prince Edward Island, New Brunswick, and the 

 greater part of Quebec and Ontario. As thus modified the limits 

 are as follows : on the north, the 48th parallel from the Gulf of St. 

 Lawrence to Lake Superior, and the international boundary thence 

 to the northwest corner of Minnesota; on the west, the western 

 boundary of Minnesota and northwestern Iowa, thence southward 

 along the 96th meridian; on the south, the southern boundaries of 

 eastern Kansas, Missouri, Kentucky, and Virginia. 



In the preparation of this edition valued assistance has been 

 received from Professor A. S. Hitchcock of the United States 

 Department of Agriculture, who has elaborated the Gramineae; 

 Mr. Oakes Ames, Assistant Director of the Botanic Garden of 

 Harvard University, who has treated the Orcliidaceae; President 

 Ezra Brainerd of Middlebury College, who has revised the genus 

 Viola; Mr. A. A. Eaton of the Ames Botanical Laboratory, who 

 has treated the technical genera Equisetum and Isoetes; Dr. J. M. 

 Greenman of the Field Museum of Natural History, who has 

 revised Senecio; Mr. W. W. Egglestox, who has revised the exceed- 

 ingly difficult genus Crataegus; and Miss Mary A. Day, Librarian 

 of the Gray Herbarium, who has given much clerical and biblio- 

 graphical assistance throughout the preparation and proof reading 

 of the text. Many of the older figures, formerly grouped in plates, 

 have been redrawn and for greater convenience placed in the text, 

 and to these have been added a much larger number of new ones 

 drawn chiefly by Mr. F. Schuyler Mathews, but in part also by 

 Professor J. Franklin Collins of Brown University and Mr. P. 

 B. Whelpley. All the illustrations of the Orcliidaceae have been 

 not only skillfully executed but generously contributed by Mrs. 

 Oakes Ames. The fact that it has been possible thus to extend the 

 illustration of the Manual has been due in great part to the interest 

 and liberality of the Visiting Committee of the Gray Herba- 

 rium. Many botanists throughout the country, notably the members 

 of the New England Botanical Club, have furnished specimens and 

 notes which have been exceedingly helpful in determining the geo- 

 graphic range and limits of variation. To all who have thus in 

 different ways aided in the preparation of the present work, the 

 editors wish to express their sincere appreciation and cordial thanks. 



At the International Botanical Congress, held at Vienna, June, 



