ROBINSON AND GREENMAN. — GENUS VERBESINA. 535 
Cent.-Am. Bot. are enumerated, with synonymy and citation of specimens, 
30 named species known to grow in Mexico and Central America. So 
rapid, however, has been the recent exploration of the regions mentioned 
that this number is already more than doubled. 
The genus is now generally conceded to be exclusively American, 
except so far as species have been introduced or naturalized in some 
parts of the Old World. Various obscure gerontogeous plants, early 
ascribed to Verbesina and enumerated in the Index Kewensis, are 
omitted from the following revision as they are with little doubt generi- 
cally distinct. 
The genus as here presented contains 109 species. More than 70% of 
these are local, and over 90% are confined to some one of the following 
regions, 
S. E. United States (S. Car. to Fla. and Ala.). . . 8 species. 
Region of the Lower Rio Grande . . ..... 2 
Sonoran Region (W. Tex. to L. Calif.and N. W. Mex.) 16 “ 
Central. and 8. Mexitg og, Sis cack wakes a 
Contxal Ametiog 0500) 4 os ayia cee cae ee 4 
N. South America (U. S. Colombia to Guiana). . . 4 © 
Brazil, Uruguay, Paraguay, Argentine Rep. . . - I1 
Andean Region (Ecuador to Chili) . ....-+ 8 
Wedndiog: oo en soaei me 
Verbesina, as a whole, reaches its highest specific diversity in the 
uplands of Central and Southern Mexico, where no less than 40% of its 
Species are endemic, The genus is conveniently divided into 12 sections, 
of which Hamulium, Platyptera, Stenocarpha, Alatipes, Pterophyton, 
Sonoricola, Ximenesia, and Pseudomontanoa are obviously natural 
stoups, Of these Hamulium, Platyptera, Stenocarpha, Alatipes, and 
Sonoricola are each composed of species of uniform or contiguous ranges. 
P. seudomontanoa, apparently unrepresented in Central America and 
W. Indies, is found in Mexico and Caribbean S. America. Ximenesia 
exhibits in the species V. australis a new instance of the interesting 
community of character between the flora of the Rio Grande region and 
that of extra-tropical S. America. : 
The sections Verbesinaria, Saubinetia, Ochractinia, and especially 
Lipactinia, must be regarded rather as provisional aggregates than 
natural or wholly satisfactory groups. In the general arrangement of 
the sections the sequence is from the large-headed to the small-headed 
forms. It may be noted that discoid heads occur only in Platyptera and 
