524 PROCEEDINGS OF THE AMERICAN ACADEMY. 



§ 2. Scales of the involucre decidedly unequal, imbricated in 2 to 4 

 rows, the outer shorter : mostly shrubs. 



* Heads (seldom numerous) borne on long pedicels (6 to 10 cm. in length) or 

 umbellately clustered at the summit of long nearly naked peduncles. 



1- Perennial herb with short thick woody stock and fibrous roots : leaves con- 

 duplicate. 



G. P. JALISCENSE, Robinson & Greenman. Scabrous-puberulent 

 throughout : middle and upper leaves oblong or narrowly elliptic, regu- 

 larly folded along the miduerve, recurved : involucral scales short, ovate, 

 finely puberulent, obtuse, scarcely or not at all ciliate. — Am. Jour. Sci. 

 ser. 3, 1. 154. — Rocky Hills about Guadalajara, Jalisco, Falmer, no. 

 310, Pr ingle, no. 5426. 



H- -1- Perennial herb from a long stout root : rameal leaves small, elliptic-oblong, 



entire. 



7. P. PARVIFOLIUM, Gray. Stems 3 dm. or more high, copiously 

 branched: stem-leaves ovate, 2 to 4 cm. long; the rameal 7 to 12 mm. 

 long, numerous : heads on relatively short erect pedicels umbellately 

 clustered at the ends of long peduncles (1 to 1.5 dm. in length) ; involu- 

 cral scales blunt, ciliate. — Proc. Am. Acad. xv. 3G ; Hemsl. 1. c. 182. — 

 Mountains of San Luis Potosi, Schaffner, no. 352, Parry & Palmer, no. 

 475 ; Durango, Palmer, no. 320 (coll. of 1896), Nelson, no. 4624. 



H- H- H- Shrub : rameal leaves large, ovate, serrate. 



8. P. subsquarrosum. Stems distinctly woody ; branches opposite, 

 scabrous-puberulent: leaves large, ovate, 7 cm. long, 3 to 3.5 cm. broad, 

 serrate, acute, rounded at the base, green and scabrous-pubescent on both 

 surfaces; petiole about 2 mm. long: heads 7 mm. broad (excl. of the 

 rays), borne on long pedicels from the upper axils or on shorter pedicels 

 in a pedunculate umbel ; involucre campanulate, the scales with obtuse 

 herbaceous tips tending to be squarrose : rays about 10, orange-yellow, 

 brownish towards the base, 1.2 cm. long, 5 mm. broad : achenes of the 

 disk-flowers slender, slightly constricted above. — Near Plateado, Zaca- 

 tecas, Dr. J. N. Rose, 2 to 4 September, 1897, nos. 2751, 3649. 



* « Heads usually numerous ; pedicels and peduncles not greatly elongated, sel- 

 dom exceeding 4 cm. in length. (Long peduncles or pedicels are occasion- 

 ally found in P. rude and P.pellitum.) 



-I- Involucral scales acute or acuminate. 

 ** Leaves ovate, cordate, subcordate, or truncate at the base. 



9. P. VERBESINOIDES, DC. luvolucral scales ovate, acuminate, very 

 unequal in length : rays about 10, linear-oblong. — Prodr. v. 608 ; Hemsl. 



