82 PROCEEDINGS OF THE AMERICAN ACADEMY. 
b. Heads erect: slender annual. 
9. P. Pringlei, Robinson, Proc. Am. Acad. xxvii. 178. 
ec. Heads erect: shrubs. 
10. P. Jorullense, Cass. “ Leaves 1 inch long, oe petioles 
6 to 7 lines long: scales of the involucre green.” Dict. i. Nat. xiii. 
57. Kleinia Jorullensis, HBK. Nov. Gen. & Spee. iv. 156, t. “B56, whence 
description. 
11. P. Nelsonii. Branching shrub, 1 to 2 feet high: stems terete, 
striate, purple: leaves chiefly opposite, rather small and distant; blade 
elliptic or oblong, obtuse, 6 to 8 lines long, 2 to 3 lines broad, rather 
gradually narrowed to a slender petiole (2 or 3 lines in length); glands 
few on the margin or often only a single one at the end of the mid-nerve : 
heads subcorymbose at the ends of the branches, 7 lines long, about 30- 
flowered ; scales of the involucre 5, linear-oblong, acute, purple especially 
toward the summit, flat, marked with 2 rows of linear glands: corollas 
dark purple, 3} inches long: achenes strongly tapering, 3 to 3} lines in 
and Jaquila, altitude 5,000 feet, 26 February, 1895, no. 2399; also 
between Nopala and Mixistepic, altitude 800 to 4,000 feet, March, 1899. 
* * Leaves rather broadly lanceolate, acute at both ends, slender-peti led 
12. P. Palmeri, Rose, Contrib. U. S. Nat. Herb. i. 338, t. 34. 
* * * Leaves narrowly elliptic- or linear-oblong, obtuse or obtusish, gradually 
narrowed to a sessile or short-petioled base. 
13. P. Seemannii, Schz. Bip. 1. ¢. 
14. P. obtusifolium, DC. 1. c. 650. 
15. P. decumbens, DC. 1. «. 
* * * * Leaves lance-linear, sessile, and amplexicaul. 
16. P. amplexicaule, Engelm. in Gray, Pl. Wright. i. 120. 
* * * * * Annuals or more commonly pate often shrubby at the base: 
leaves very narrow; truly linear or subulate, or lance-linear and acute OF 
acutish, sessile or suhaeeiite: but not edison i 
+ Mexican species: corolla shallowly and regularly 5-toothed ; teeth deltoid : 
achenes 24 to 34 lines long: involucral scales green or glaucous, not dark 
purple. 
17. P. scoparium, Gray. Leaves truly linear or terete, half @ 
line in breadth: peduncles inch or more in length. — PI. Wright. i. 119. 
iB.:-P. pausodynum. Shrub: stems geniculate, ‘cated, covered 
with smooth reddish brown cortex: branchlets straight, erect, sulcate- 
angulate, glaucescent : leaves scattered, linear-lanceolate, narrowed to a0 
obtusish apex, attenuate at the base to a short petiole, slightly succulent, 
