MONOGEAPH OF THE NORTH AND CENTRAL 



AMERICAN SPECIES OF THE GENUS 



SENE CIO— PART II 1 



J. M. GREENMAX 



Curator of the Herbarium of the Missouri Botanical Garden 

 Associate Professor in the Henry Shaw School of Botany of 



Washington University 



Introduction 



The study upon which this monograph is based was begun 

 nearly twenty years ago, at which time the author was an 

 Assistant at the Gray Herbarium of Harvard University. 

 Nearly every collection of any considerable size which came 

 to the Herbarium, particularly from western United States, 

 Mexico, and Central America, contained specimens of Senecio, 

 many of which were either undetermined or referred doubt- 

 fully to some obscure or little known species. The identifica- 

 tion of such material was often a laborious task, since all 

 species recorded from a given region had to bo listed and 

 then specific identity established by a process of elimination. 

 The available publications for such work were De Candolle's 

 'Prodrome,' Gray's 'Synoptical Flora,' and Hemsley's 

 splendid contribution to the systematic literature of the 

 botany of Mexico and Central America in the 'Biologia 

 Centrali- Americana ' ; but the results obtained were often 

 very unsatisfactory, because of the large number of new 

 species published in scattered papers during the two decades 

 following the appearance of the 'Synoptical Flora' and the 

 'Biologia.' 



It was felt, therefore, that a revision of the genus, in the 

 light of recent and more complete collections, which have 

 accumulated from the numerous botanical explorations in 

 different parts of North America, would.be helpful to those 

 concerned with this difficult group of plants and especially in 

 the organization of material in different herbaria. A critical 

 study of Senecio with the view of publishing eventually a 



1 Issued October 8, 1915. 

 Ann. Mo. Bot. Gard., Vol. 2, 1915 



(573) 



