a ee See ae SM See Tey a ers nae Mee ap et em 
Se ree = ae 
Blake — A Revision of the Genus Viguiera 5 
Jeffrey for his assistance and the use of his laboratory, in connection 
with some investigations in the anatomy of Viguiera and related 
genera. 
III. RELATIONSHIPS AND SUBDIVISIONS 
The very close relationship between Viguiera HBK., Helianthus 
L., and Tithonia Desf. has been recognized by nearly all authors, 
and their differences have been well summarized by Bentham. As 
additional species of other genera of this group have been made 
known, their alliance with Viguiera has become more evident, 
while other related but distinct genera have been described, until 
the genus Viguiera now stands as the focus and probable point of 
origin of a closely related group of seven genera. These are, in 
order of publication: Helianthus L. (1753), of about 80 species, 
ranging from Canada to Peru; Tithonia Desf. (1789), of Mexico 
and: Central America, with about 8 valid species; Viguiera HBK. 
(1820), of some 120 species, from Nevada to Argentina; Heliomeris 
Nutt. (1848), the Gymnolomia of authors in great part but not of 
HBK.., of some 36 species, ranging from Montana to Ecuador, with 
one species in Georgia and one in Brazil; Hymenostephium Benth. 
(1873), of 4 species, from Mexico to Colombia; Haplocalymma 
Blake (1916), a Mexican monotype; and Syncretocarpus Blake 
(1916), of two closely related Peruvian species. All of these are 
confined to the American continent or immediately adjacent 
islands, the only at all outlying forms being a variety of a Lower 
Californian Viguiera on Socorro Island, and another variety of a 
Viguiera found in Cuba, where perhaps introduced in early times 
from Yucatan. All these genera are so nearly related that in a 
broad treatment of Composite genera their union would be neces- 
sary, with the exception of Syncretocarpus; nevertheless they 
show, with the exception of Heliomeris (“ Gymnolomia ”’ of auth.), 
of which more will be said in the sequel, sufficiently important and 
constant technical characters to be retained as distinct groups 
whatever the scheme of classification adopted. The really inter- 
mediate species are very few, and but little advantage could follow 
from their union. Discussion of their relationships will be facili- 
tated by the introduction at this point of a synoptical table of the 
essential characters, on the basis of which these groups are now gen- 
erally separated. 

