438 PROCEEDINGS OF THE AMERICAN ACADEMY. 
II. REVISIONS OF ALOMIA, AGERATUM, AND OXYLOBUS. 
By B. L. Rosprnson. 
THE following treatment has been based chiefly upon an intensive 
study of the pertinent material in the Gray Herbarium, but much aid 
has been derived from a series of photographs, taken at various Euro- 
pean herbaria in 1905 and 1910, representing the types of nearly all 
the recognized species of Alomia and Ageratum not originally described 
from the Gray Herbarium. There has been no opportunity to test 
the keys and descriptions by a re-examination of the extensive material 
in foreign collections, but through the kindness of Messrs. Coville 
and Maxon the writer has been permitted to borrow and study the 
representation of Alomia and Ageratum from the National Museum at 
Washington, a considerable privilege for which he would express great- 
ful appreciation. The writer is also much indebted to Mr. John 
Donnell Smith for the loan of Ageratum and Alomia from his rich— 
personal herbarium, and to Mr. A. B. Rendle of the British Museum 
of Natural History for the critical comparison establishing beyond 
doubt the identity of Ageratum Houstonianum Mill. Miss M. A. Day 
and Miss E. M. Vincent of the Gray Herbarium staff have given 
bibliographical aid. 
It may be said in a general way that the species of these genera do 
not tend to serious intergradation, except in the case of Ageratum 
conyzoides L. and A. latifolium Cav. (not Hemsl.), where separation 
though easily made seems pretty artificial, and on the other hand the 
several species which are closely allied to the highly variable A. 
corymbosum Zuccag. and are distinguished chiefly by such characters — 
as leaf-contour, pubescence, ete. | 
It must be frankly admitted that the treatment of the South 
American species is very sketchy, being derived from wholly inade- 
quate material. It is highly pl »bable that furth expt tion f north- 
ern South America and of Brazil will bring to light many further 
species, and perhaps considerably modify our present views as to the 
distinctness of those already known. 
1. Revision or THE Genus ALOMIA. 
Tue tropical American genus Alomia is a convenient rather than @ 
convincingly natural group of species. Depending for its separation 
