12 Contributions from the Gray Herbarium 
and northern Argentina, and the uplands of Brazil, Paraguay, and 
Uruguay. 
The distribution of Helianthus as a genus is quite different. Of 
the species now known, approximately 80 in number, some 65 are 
found in the United States, about equally divided between east and 
west, a few ranging north to Canada. In Mexico and Lower Cali- 
fornia occur about eight species (excluding H. parviflorus HBK. 
and H. mexicanus (Walp.) Hemsl., whose status as members of the 
genus can scarcely be considered as sufficiently made out as yet), 
all of which, with the exception of H. similis already discussed, are 
represented by identical or allied species in the adjacent United 
States, and are therefore perhaps to be considered as immigrants 
from that region. None extends further south than the elevated 
regions of San Luis Potosi; in southern and central Mexico, where 
Viguiera displays its greatest: luxuriance in species and groups, the 
genus is entirely absent, —the plant described by Greenman as Heli- 
anthus oaxacanus being a good Viguiera of the series Maculatae, — 
nor is it found again until the mountains of Ecuador and Peru are 
reached. These, the only South American species of Helianthus, — 
Philippi’s Chilean species, most and perhaps all of which belong to 
Viguiera, and a few described by the older authors being disre- 
garded as too uncertain, — are about ten in number. Although in 
general features for the most part very close to the Viguieras (sub- 
series Huaureae) of the same region, they possess the typical pappus 
of Helianthus, of two quickly deciduous paleaceous awns, and are un- 
doubtedly as truly members of the latter genus as its United States 
representatives. A small group of Viguiera from the same region 
lanceolata, V. pazensis, and V. Pflanzii), closely similar in 
habit, has the normal pappus of Viguiera, but the awns and some- 
times some of the squamellae tend to be more or less deciduous. 
These species, however, are best retained in Viguiera, since the 
deciduous character even of the awns is by no means a fixed one. 
At this point, however, as in the case of Helianthus similis of 
Lower California, the two genera approach one another very 
closely, and it is to these two groups of Viguiera — the subseries 
Euaureae of South America, and the series Dentatae (with the Gram- 
matoglossae ?) of Mexico and Lower California — that I am dis- 
posed to look for the points of origin of the genus Helianthus as we 
know it today. It is also possible that the series Maculatae of 
fal i ee ae mh eee 

