522 PROCEEDINGS OF THE AMERICAN ACADEMY. 
tively short tube, rather long throat and 5 ovate teeth. Appendages of 
the style-branches short. Disk-achenes laterally compressed, the ray- 
achenes triangular, both wingless; pappus of several to many unequal 
awns; these sometimes slightly connate below. — Perennial herbs, un- 
dershrubs or tall shrubs, with opposite entire, serrate, or crenate (not 
lobed) 3-nerved usually scabrous leaves, and solitary to umbelliform- 
corymbose heads. Flowers yellow. — Ind. Sem. Hort. Gotting. 1880; 
Linnea, vi. (1831), Lit.-Ber. 73; DC. Prodr. v. 608 (excl. synon. Schis- 
tocarpha) ; Benth & Hook. f. Gen. ii. 8377; Hemsl. 1. c. 180 ; Hoffm. in 
Engl. and Prantl, Nat. Pflanzenf. iv. Ab. 5, 236. — DeCandolle in 
- 1836‘ enumerates 8 species, Bentham and Hooker in 1873 ascribe to the 
genus 10 species, Hemsley in 1881 enumerates 12 named species within 
the limits of the Biologia Centrali-Americana, and Hoffmann in 1890 
places the species at 13, —a number which is just doubled in the present 
revision. The species are chiefly local, and are most numerous in South- 
ern and Central Mexico. The genus as a whole ranges from Northern 
Mexico to the United States of Colombia. 
§ 1. Scales of the involucre subequal, herbaceous, uniseriate or ob- 
scurely biseriate: heads few, long-peduncled ‘from the ends of the 
branches; ligules 8 to 12, showy for the genus, 1 to 1.4 cm. in length: 
herbaceous or nearly so with several mostly decumbent stems from 4 
thick lignescent root or stock. 
% Involucral scales covered with a rather coarse somewhat spreading pubescence 
and often ciliate. ; 
« Involucral scales broad, ovate-oblong, obtuse or rounded at the apex- 
assurgent simple 1-2-headed branches: leaves oval or elliptical, obtuse, 
pubescent, crenate-serrate, rugose above, scarcely paler beneath, rounded 
at the base, 1.5 to 2 em. long, 1.2 to 1.8 cm. broad; petioles coarsely 
pubescent, 8 mm. long: peduncles 3 to 8 cm. long; involucral scales 
about 10: rays about as many, elliptical, 1 cm. long, 5 to 6 cm. broad. — 
Proc. Am. Acad. xv. 36; Hemsl. Biol. Cent.-Am. Bot. ii. 182. <a 
tains of San Luis Potosi, Schaffner, no. 302, Parry & Palmer, no. 459; 
also between Sta. Gertrudis and Sta. Teresain the Sierra Madre of 
Tepic, Rose, nos. 2077, 8313; also a doubtful specimen from the Siert 
of Guanajuato, altitude 2,000 m. Guillemin-Tarayre. Likely to P° 
reduced to the following. 
_ 2*. P. Barctayanum, DC. This species, said to be a subscandent 
_ dershrub, does not differ materially from the preceding in other deseridé 
va 1. P. renettum, Gray. Stems prostrate, spreading, with numerous 
t un- 
