522 PEOCEEDINGS OF THE AMERICAN ACADEMY. 



lively 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. 1830; 

 Liunaja, vi. (1831), Lit.-Ber. 73 ; DC. Prodr. v. 608 (excl. synon. Schis- 

 tocarpha) ; Benth & Hook. f. Gen. ii. 377 ; 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 a 

 thick lignescent root or stock. 



* Involucral scales covered with a ratlier coarse somcwliat spreading pubescence 



and often ciliate. 

 -t- Involucral scales broad, ovate-oblong, obtuse or rounded at the apex. 

 1. P. TENELLUM, Gray. Stems prostrate, spreading, with numerous 

 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 cm. long, 1.2 to 1.8 cm. broad; petioles coarsely 

 pubescent, 3 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. — Moun- 

 tains oi San Luis Potosi, Schaffner, no. 302, Parry & Palmer, no. 450 ; 

 also between Sta. Gertrudis and Sta. Teresa in the Sierra Madre of 

 Tepic, Pose, nos. 2077, 3313; also a doubtful specimen from the Sierra 

 of Guanajuato, altitude 2,000 m., Guillemin-Tarayre. Likely to be 

 reduced to the following. 



2*. P. Barclayanum, DC. This species, said to be a subscandent un- 

 dershrub, does not diflfer materially from the preceding in other described 



