iv TKEFACE. 



country have made it necessary to annotate and to some extent to revise 

 the portions written by Drs. Gray and Watson. Every effort, however, 

 has been made to indicate the place and extent of such alterations, and, 

 wherever consistent with the brevity necessary in the work, to show the 

 nature of the original manuscript and reason for change. Both Dr. Gray 

 and Dr. Watson, in the course of theii- i)reparation of the present work, 

 issued from time to time preliminary papers, such as their revisions of 

 the genera Ranunculus, Delphinium, Asimina, Viola, Lesquerella, Draha, 

 &c., so that their views upon these groups are already to a considerable 

 extent known to science. The editor has therefore felt somewhat greater 

 liberty in revising the manuscript of such groups in the light of later 

 literature and recent collections.. All species of wliich the names or 

 descriptions have been altered in any way, as well as recent species 

 which have been inserted by the editor, are marked with the asterisk (*). 

 The authorship of the different groups is indicated at the beginning of 

 each order. For additional clearness in the Cruciferce, the authorship is 

 also given in each genus. 



In the citation of authorities and of literature, as well as in the matter 

 of nomenclature, the present issue has been made as far as possible to 

 conform to the portions of the work already published. Well known 

 generic names have in some cases been conserved on the ground of usage, 

 notwithstanding technical lack of priority. This is especially the case 

 with names which have received the recent indorsement of the botanists 

 of Kew and Berlin. In the matter of specific names, the aim has been 

 to follow the so-called Kew Rule, except where it leads to indefiniteness. 

 The recent efforts .to place botanical nomenclature upon a different basis 

 have led to the hasty restoration in American botany of a considerable 

 number of names, such as Ncckeria, Capnorchis, Bcurera, &c., which have 

 been again as quickly abandoned. The detailed citation of these names, 

 ■and the numerous combinations to which they have led, forms no part of 

 Dr. Gray's original plan, shown by the following words from his fu-st 

 Preface : " Compactness being essential, only the leading synomymy and 

 most important references are given, and these briefly." An effort has 

 been made, however, to cite as synonyms such names as are at present 

 indorsed by the Rochester and Madison Rules, and are included in the 



