PREFACE. 



This volume commences where the Flora of North America by Torrey 

 and Gray stopped, thirty-five years ago, namely at the close o£ the great 

 order of Compositae ; and the present part comprises the remaining 

 Gamopetalee. It is intended to complete this Synoptical Flora in two 

 volumes, of about 1200 pages each ; the first to cover the ground which 

 was gone over in the work referred to (now wholly out of print as well 

 as antiquated), that is, to contain the orders from Ranunculaceae to Com- 

 positae, newly elaborated. The next ensuing part of the present volume 

 will be devoted to the Apetalse and Gymnospermss, and the final portion 

 to the Monocotyledones and the Vascular Cryptogamia. 



Botanists will need no particular explanation of the plan of this work. 

 Geographically it comprises the United States and all the North Amer- 

 ican continent and islands northward, Greenland excluded. The series 

 of Natural Orders adopted is that of Bentham and Hooker's Genera 

 Plantarum. The generic characters are given synoptically, but with 

 essential completeness, at the beginning of each order. The characters 

 of sections of genera, when of comparatively high rank, are designated by 

 the sectional mark (§) and printed in the larger type ; and those of 

 first "importance, such as may be termed subgenera, are distinguished by 

 having a substantive name. Subsections, and also primary divisions 

 when of low rank, are in small type. Such subdivisions are very freely 

 made, for convenience of analysis and to save repetition of identical 

 phrases under the included species ; and they are preferred to artificial 

 keys to the species, because enabling these to be grouped more naturally. 

 If somewhat less facile for rapid determination, they are more ex- 

 haustive and less liable to mislead ; and they permit the ultimate specific 



