CONTRIBUTIONS FROM THE GRAY HERBARIUM OF HARVARD 
UNIVERSITY.— NEW SERIES, No. XLII. 
Presented by B. L. Robinson, May 14, 1913. Received June 24, 1913. 
I. A GENERIC KEY TO THE COMPOSITAE-EUPATORIEAE, 
By B. L. Rosinson. 
It is now more than twenty years since the genera of the Eupatorium 
tribe were keyed by Hoffmann in Engl. & Prantl, Nat. Pflanzenf. iv. 
Ab. 5 (1890). During this interval several genera have been added 
to the tribe, some few have been definitely removed from it to other 
tribes of the Compositae, two (Brachyandra and Addisonia) have been 
reduced, and certain sections of genera have come to appear worthy 
of generic rank within the tribe. In consequence the key of Hoffmann, 
“though excellent for its time, is now unsatisfactory and far from com- 
plete. The one here offered, though drawn up after some years’ 
study of the group, is put forth rather as a convenient working hy- 
pothesis than a finished or monographic product. 
In the Eupatorium tribe, as elsewhere in the Compositae, generic 
distinctions, though essential for classification, often seem pretty arti- 
ficial and the more precisely they are stated the greater of necessity 
becomes the artificial or arbitrary element. A re-examination of the 
technical characters relied upon by the older authors discloses many 
exceptions and transitions. On the other hand persistent attempts 
secure a more natural classification by relying in larger measure 
upon habital traits have proved even more disappointing. These, 
while fairly convincing among plants of a circumscribed area, quickly 
lose any statable definiteness in dealing with the species of the world. 
One is in consequence forced to a restatement of the distinctions of 
pappus, achenes, anther-tips, and involucral-bracts as yielding after 
all the most practical basis for classification in the up. 
In order to employ these more technical features effectively some 
explanation and definitions are necessary. 
The pappus of the Eupatorium tribe offers a wide variety, including 
nearly all forms found in the Compositae. Scales, distinct or connate, 
