PREFACE. 



Of the Synoptical Flora of North America Dr. Gray published, 

 in 1878, Volume 11. Part 1, comprising the gamopetalous ordei-s after 

 the Composite^, and following rather closely, in the sequence and limita- 

 tion of orders, Bentham & Hooker's Genera Plantaruim. The object 

 in thus beginning with the second portion of the work was to monograph 

 first such orders as had not been treated in Torrey & Gray's Flora of 

 North Aisierica.. This earlier work, published Ijetween 1838 and 1843, 

 included the polypetalous orders of North America and the Gamo'pctalcD 

 through the Compositce. In planning the Synoptical Flora, Dr. Gray 

 left the orders thus treated to form the subject matter of Volume I. In 

 1884, he published Part 2 of tliis first volume, incluchng the GamopctalcK 

 from the Caprifoliacece through the Compositce. In 1886, the two por 

 tions, thus published, were revised and amplified by Dr. Gray, and 

 reissued by the Smitlisonian Institution. K \ S c e \\ a \v (. o \a ^ ^ \ • V . "^ \ 



In his last years Dr. Gray was engaged in monographing the earlier 

 polypetalous orders for Volume I. Part 1. In this work he had finished 

 at the time of his death most of the orders to, but not including, the 

 Leguminosce. The treatment of several large groups, however, sucli as 

 the CrucAfcrcv^ CaryopkyUacece, Hypericaceoe, Rhamnacece^ &c., liad for 

 various reasons been deferred. After Dr. Gray's death tlie AAork was 

 continued by Dr. Sereno Watson, who prepared eleven genera of the 

 Cruclferce, including several of the largest and most diilieult of tlie order. 

 After the death of Dr. Watson, in 1892, the work was intrusted to the 

 present editor. 



The time which has necessarily elapsed since the inception of the work 

 by Dr. Gray and the very considerable botanical activity throughout our 



