Blake — A Revision of the Genus Viguiera 3 
the persistent pappus, characters which, although leaving much to 
be desired, have not been improved upon or strengthened by any 
later worker on the genus. The species were said to be about 60 
in number. 
In 1881 Hemsley ' listed 20 species of the genus, two being un- 
named, from Mexico and Central America, and two years later 
Gray? published important notes on several species. Baker’s 
treatment * of 1884, in the Flora Brasiliensis, enumerating 29 
species, is the latest general conspectus of any considerable portion 
of the genus to be published. Its arrangement, however, is purely 
artificial. Baillon ¢ in 1886, in his Histoire des Plantes, following 
out his general practice of reduction of genera in the family, united 
Tithonia, Viguiera, and the more distantly related Flourensia and 
W yethia under Helianthus L. Hoffmann in 1890, in the Pflanzen- 
familien, gave the number of species as 60-70, but contributed noth- 
ing to our knowledge of the group. More recently a considerable 
number of new species have been described from Mexico, chiefly by 
Robinson, Greenman, Brandegee, and Rose, and from South Amer- 
ica, chiefly by Hieronymus and Chodat, and in 1913 some rectifica- 
tion of the generic lines in this group, which had become somewhat 
confused, was attempted by the present writer * in connection with 
a revision of the genus Encelia. The latest attempt at a redefini- 
tion of the generic line to be drawn between Viguiera and Helian- 
thus, made by Prof. T. D. A. Cockerell,”? cannot be considered a very 
successful one. Prof. Cockerell proposes as a possible solution of 
our difficulties in this regard a study of the varying color-changes 
induced in the rays by treatment with a solution of potassium 
hydrate. Prof. Cockerell’s observations were based on some half- 
dozen species of Helianthus and on a single species of Viguiera out 
of its total of some hundred and forty, and can scarcely be con- 
sidered to promise much for.a more natural classification, since he 
found that not even all the perennial species of Helianthus agreed 
in their response to KOH, while the annual species agreed with the 
single Viguiera (itself a perennial) and with a miscellaneous collec- 
? Hemsl. Biol. Centr.-Am. a ii. 177-179 (1881). 
id ; Gray, Proc. Am. Acad. xix. 5 (1883). 
* Baker in Mart. Fl. Bras. vi. pt. 3. 217-229. t. 66 (f. 2)-68 (1884). 
: . Pl. viii. 46, 201 
* O. Hoffm. in Engl. & Prantl, Nat. Pflanzenfam. iv. pt. 5. 235 (1890). 
® Blake, Proc. Am. Acad. xlix. 346-349, 374-376 (1913). 
. Cockerell, Torreya xv. 11-16 (1915). 
