114 



COULTER AND ROSE 



Dr. T. Altimarano, Director of the Medical Institute of Mex- 

 ico, has also been of much service in contributing specimens, 

 chiefly from the mountains about the Valley of Mexico. 



In the present paper this new material is published, and also 

 revisions of certain genera which are now better understood. 

 One of the most interesting facts is the great increase in our 

 knowledge of Prt'onosciadtum, a genus established in 1888 as 

 containing three species, which recent collections have increased 

 to fifteen. The largest genus of the region, Eryngium, is now 

 being studied by Mr. Hemsley. His descriptions of several 

 new species, published in Hooker's Icones, are herein translated 

 and republished, together with tracings of the plates, made by 

 Miss Anna Snyder. The genus Ai'racacia also has received 

 large additions, seven new species being described in the present 

 paper, and others previously. The genus, however, has lost 

 several species to Tatisc/na, the generic boundary between the 

 two being more definitely understood. It is also of interest to 



Genera added since Hemsley. 



