870 COMPOSITAE (COMPOSITE FAMILY) 



4. C. TECT6RUM L. Slender, branching from the base, 2-4 

 dm. high ; leaves narrow, runcinate, often sagittate-auriculate ; 

 heads small, in a loose panicle ; achenes fusi- 

 form^ attenuate above, the ribs upwardly sca- 

 brous. In fields, Ont., Mich., and Neb.; and 

 on ballast eastw. July-Sept. (Adv. from Eu.) 

 1*. C. tectorum. *IO. 1038. 



Head x 2 / * C. BiENNisL. Somewhat pubescent, 6-8 dm. 



Achene xl%. n ^> leafy ; leaves runcinate-pinnatifid ; heads 

 rather large, 2-4 cm. broad, corymbose ; achenes 

 13-nerved, glabrous, attenuate above. Locally in fields and waste 1034. c. biennis. 

 places, N. E. to Pa. and Mich. (Adv. from Eu.) FIG. 1034. Achene xi%. 



105. PRENANTHES [Vaill.] L. RATTLESNAKE-ROOT 



Heads 5-30-flowered. Involucre cylindrical, of 6-14 linear bracts in a single 

 row, and a few small bractlets at base. Achenes short, linear-oblong, striate 

 or grooved, not contracted at the apex. Pappus of copious whitish, straw- 

 colored, or brownish rough capillary bristles. Perennial herbs, with upright 

 leafy stems arising from spindle-shaped (extremely bitter) tubers, very variable 

 leaves, and racemose-panicled mostly nodding heads. Flowers in late summer 

 and autumn. (Name from Trpyvjs, drooping, and &v8-n, blossom.) NABALUS 

 Cass. 



* Heads rather broad, 25-35-Jlowered, in a corymbose panicle. 



1. P. crepidinea Michx. Somewhat smooth ; stem stout, 1.5-2.7 m. high, 

 bearing numerous nodding heads in loose clusters ; leaves large (1.6-3 dm. 

 long), broadly triangular-ovate or halberd-form, strongly toothed, contracted 

 into winged petioles; flowers cream-color; pappus brown. (Nabalus DC.) 

 Rich soil, w. N. Y. to Minn., and southw. Sept., Oct. 



* * Heads slender, 8-15-flowered, in a long raceme-like or thyrsoid inflorescence; 

 stems simple ; cauline leaves sessile ; pappus straw-color. 



*- Inflorescence pubescent, strict; heads nearly erect, 12-15-flowered. 



2. P. racem&sa Michx. Stem 0.2-1.5 m. high, smooth and glaucous, as well 

 as the oval or oblong-lanceolate denticulate leaves; the lower leaves tapering 

 into winged petioles (rarely cut-pinnatifid) , the upper partly clasping ; heads in 

 crowded clusters ; flowers purplish. (Nabalus Hook.) River-banks and prai- 

 ries, e. Que. to Alb., s. to N. B., n. Me., Great L. region, Mo., S. Dak., and Col.; 

 also in marshes of s. N. Y. and n. N. J. Aug., Sept. Var. piNNATfriDA Gray. 

 Leaves all lyrately pinnatifid. Marshes, s. N. Y. and n. N. J. ; also in Ont. 

 (according to Macoun). 



3. P. aspera Michx. Stem 0.6-1.3 m. high, rough-pubescent, as well as the 

 oval-oblong or broadly lanceolate toothed leaves; upper leaves not clasping; 

 heads in small clusters ; flowers larger, cream-color. (Nabalus T. & G.) Dry 

 prairies and barrens, O. to S. Dak. , and southw. Aug. , Sept. 



- - Wliole plant glabrous; heads nodding, S-12-Jlowered; thyrse looser. 



4. P. virgata Michx. (SLENDER R.) Slightly glaucous ; stem 6-12 dm. 

 high, prolonged into a naked and slender spiked raceme (4-6 dm. long); heads 

 clustered and mostly unilateral ; leaves lanceolate, acute, closely sessile, the 

 upper reduced to bracts, the lower toothed or pinnatifid ; involucre (purplish) 

 of about 8 bracts. (Nabalus DC.) Sandy pine barrens, N. J. to Fla. Sept., 

 Oct. 



6. P. mainSnsis Gray. Stem 0.5-1 m. high, leafy ; leaves as in no. 2, but the 

 radical ovate and more abruptly narrowed to the short petiole ; heads persistently 

 drooping on slender pedicels. St. John and Aroostook valleys, Me. and N.B. 

 Aug., Sept. Perhaps a hybrid between nos. 2 and 8. 



