qo6 



PLOZA. 



nearly leafless, 3-9 cm. high. Leaves villous or hirsute, the basal and lower ones 

 obovate or spatulate, denticulate, or entire, obtuse, 5-15 em. long, usually narrowed 

 into petioles; stem leaves mostly sessile, oblong or oval, obtuse or acute, the upper 

 gradually smaller; heads 10-18 mm. broad; peduncles glandular and canescent, 

 slender; involucre about 8 mm. high, somewhat canescent, bracts linear lance- 

 olate, acute, with several very small outer ones. In dry soil, Mass. to Out., 111., 

 Fla. and Tex. July-Sept. 



16. Hieracium longipilum Torr. Long-bearded Hawkweed. (I. F. f. 

 3575.) Stem, at least its lower portion, and leaves densely covered with long 

 brown rather rigid bristly hairs 1-2.5 cm. long, arising from papillae. Stem very 

 leafy below, stiff, simple, 6-10 dm. high; basal and lower leaves spatulate or ob- 

 long, obtuse, mostly entire, 8-16 cm. long, narrowed into margined petioles, the 

 upper lanceolate or spatulate, mostly sessile; heads 16-20 mm. broad; peduncles 

 tomentose and glandular; involucre 8-io mm. high, bracts linear-lanceolate, acu- 

 minate, with several short subulate outer ones. Prairies and dry woods, Ont. to 

 Minn., 111., Kans. and Tex. July-Sept. 



22. NABALUS Cass. (See Appendix.) 



Perennial, herbs with alternate, mostly petioled, dentate lobed or pinnatifid 

 leaves, or the upper auriculate and clasping, and numerous small heads of ligulate 

 white yellowish or purplish flowers in open or spike-like terminal panicles, or also 

 in axillary clusters, usually drooping. Involucre cylindric, usually narrow, its 

 principal bracts in I or 2 series, nearly equal, with a few smaller exterior ones at 

 the base. Receptacle flat, naked. Rays truncate and 5-toothed at the summit. 

 Style-branches slender. Achenes oblong or narrowly columnar, truncate, terete or 

 4-5 -angled, mostly io-ribbed. Pappus of copious rather rigid simple white to red- 

 dish-brown bristles. [Modern Latin, from an Indian name for Rattlesnake-root.] 

 About 20 species, natives of America and Asia. Besides the following, another 

 occurs in northwestern Am. 



* Bracts of the involucre glabrous, or with a few scattered hairs. 

 Heads 5-7 flowered; involucre very narrow, light green, 2 mm. thick ; pappus light 



straw-color. 1. N. altissimus. 



Heads 8-16 flowered; involucre broader, green, purple or glaucous, 3-6 mm. thick. 



Leaves, or some of them, lobed, divided, or pinnatifid ; involucre about 3 mm. thick./ 

 Pappus deep cinnamon-brown. 2. N. albus. 



Pappus straw-color or light brown. 

 Inflorescence paniculate. 



Involucral bracts with some stiff hairs, obviously shorter than the pap- 

 pus; panicle-branches divergent. 3. N. serpent at iuL 

 Involucral bracts glabrous, equalling the pappus ; panicle-branches 

 ascending, or erect. 4. N. trifoliolatus 

 Inflorescence thyrsoid or glomerate. 



Leaves palmately lobed or divided; northern. 5. N. nanus. 



Leaves pinnately lobed or pinnatifid ; southern. 6. N. virgatus. 

 Leaves irregularly dentate or denticulate, oblong ; plant tall. 3. N. serpentarius. 

 Leaves entire or denticulate ; plant low, alpine ; involucre 5-6 mm. thick. 



7. N. Boot tit. 

 * * Bracts of the involucre hirsute-pubescent. 

 Inflorescence narrowly thyrsoid; heads 8-16-flowered. 



Leaves and stem rough-puberulent or scabrous. 8. N. asper. 



Leaves and stem glabrous, glaucous. 9. N. racemosus. 



Inflorescence corymbose-paniculate; heads 20-25-flowered. 10. N. crepidineus. 



i. Nabalus altissimus (L.) Hook. Tall White Lettuce. (I. F. f. 3576.) 

 Glabrous, or sparingly hispidulous, not glaucous; stem slender, 1-2 m. high. greea, 

 or sometimes purplish. Leaves thin, hastate, cordate, ovate, or the uppermost 

 lanceolate, entire, denticulate, dentate or palmately lobed or divided, most of them 

 long-petioled, the larger sometimes 15 cm. long; heads very numerous, in a nar- 

 row panicle, and often in axillary clusters. 5 7-tlowered. pendulous, about 4 mm. 

 broad; inflorescence often narrow; involucre narrowly cylindric, 10-18 mm. long, 

 about 2 mm. thick, green, glabrous, its principal bracts about 5; flowers greenish 

 or yellowish white. In woods and thickets, Newf. to Manitoba, south to Ga. and 

 Tenn. July-Oct. [Prenanthes altissima L.] 



