Blake — A Revision of the Genus Viguiera 11 
generally passed as H. dealbatus Gray. With the general habit of 
a Viguiera, but the involucre more nearly of a Helianthus, it has a 
pappus of several (3-8) variously unequal paleaceous scales, which 
at maturity are strongly deciduous, so that its reference to Helian- 
thus seems the best disposition that can be made of it. A full ac- 
count of its synonymy will be found in the list of excluded species 
under V. nivea. The other plant, V. smilis Brandegee, has the 
habit and nearly the involucre of the series Dentatae of Viguiera, 
with a Viguieroid pappus of two awns and several short squamellae. 
The whole pappus, however, is absolutely deciduous from the thick 
and almost glabrous mature achene, and the species, although pre- 
sumably a late derivative and still retaining strong evidence of its 
Viguieroid progeniture, seems to be more at home in Helianthus. 
The distribution of the two genera is of considerable significance 
in connection with their probable evolutionary history. That of 
Viguiera ' may be summarized as follows. With extreme northern 
limits in Inyo County, California, and Lincoln County, Nevada, 
where two species are found, the genus is represented by eight 
species in Lower California and adjacent California and Arizona. 
From western Texas, New Mexico, and Arizona, where two species 
are found, it extends south through all the elevated regions of 
Mexico, reaching its greatest diversity in the area from Durango 
to Oaxaca, wherein occur members of all the groups found north 
of the Isthmus, forming by far the richest display of diversified 
forms in the genus, although as many species are found in Brazil. 
A few scattering species of the section Diplostichis continue the 
genus to Colombia and Venezuela, where an apparent break in dis- 
tribution occurs. From the mountains of Ecuador southward to 
Bolivia occur an increasing number of species, all belonging to one 
section (Paradosa); only three or four are known from Chile, and 
but few more from northern Argentina. In the mountainous areas 
of Goyaz, Matto Grosso, and Minas Geraes and southward to 
Uruguay and Paraguay occur some 47 species, representing the 
subgenus Yerbalesia and the sections Paradosa and Trichophylla of 
Calanticaria. The genus is then chiefly one of Lower California, 
central and southern Mexico, the mountains of Ecuador to Bolivia 
1 The statement of the range of the Srey here presented is based aly 
oo pappus-bearing members, which are those most closely related % 
