ra 
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. 
+ Perennial herb with short thick woody stock and fibrous roots: leaves con- 
duplicate. 
6. P. saLiscensE, Robinson & Greenman. Scabrous-puberulent 
throughout: middle and upper leaves oblong or narrowly elliptic, regu- 
larly folded along the midnerve, 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, Palmer, no. 
310, Pringle, no. 5426. 
+ + Perennial herb from a long stout root: rameal leaves small, elliptic-oblong, 
entire. 
7. P. parvirouium, 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. 36; Hemsl. 1. c. 182.— 
Mountains of San Luis Potosi, Schaffner, no. 352, Parry & Palmer, 00. 
475; Durango, Palmer, no. 820 (coll. of 1896), Nelson, no. 4624. 
ia + + + 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- 
om exceeding 4 cm. in length. (Long peduncles or pedicels are occasion: 
ally found in P. rude and P. pellitum.) 
+ Involucral scales acute or acuminate. 
++ Leaves ovate, cordate, subcordate, or truncate at the base. 
9. P. verBzsinoipes, DC. Involucral scales ovate, acuminate, Very 
unequal in length: rays about 10, linear-oblong. — Prodr. v- 608 ; Hemsl. 
