870 COMPOSITAE (COMPOSITE FAMILY) 



4. C. TECTORUM L. Slender, branching from the base, 2 4 

 dm. high ; leaves narrow, runcinate, often sagittate-aiii-iculate ; 

 heads small, in a loose panicle ; achenfn fusi- 

 form, attenuate above, the ribs upwardly sca- 

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

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



lObb. C. tectorum. FlG. 1033. • 



Head X 2/ ^' C biennis L. Somewhat pubescent, 6-8 dm. 



Achene x'lV ^ig^i leafy ; leaves runcinate-pinnatifid ; heads 

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

 13-nerved, glabrous, attenuate above. — Locally in fields and waste I0o4. c. biennis, 

 places, N. E. to Ta. and Mich. (Adv. from Eu.) Fig. 1034. Achene x 11/3. 



106. PRENANTHES [Vaill.] L. Rattlesnake-root 



Heads 5-30-flowered. Involucre cylindrical, of 5-14 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 upriglit 

 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 irp-qvTjs, drooping, and di>67], blossom.) Nabalus 

 Cass. 



* Heads rather broad, 2o-Sb-flowered, 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 (1.5-3 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, S-lo-Jlowered, in a long raceme-like or thyrsoid inflorescence ; 

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



•<- Inflorescence pubescent, strict; heads nearly erect, 12-ld-flowered. 



2. P. racemosa 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 iu 

 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. piNNAxfFiDA Gray. 

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

 (according to Macoun). 



3. P. aspera Michx. Stem 0.5-1.3 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. (Xahalus T. & G.) — Dry 

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



-t- H- Whole plant glabrous ; heads nodding, S-\2-flowered; thyrse looser. 



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

 high, prolonged into a nake<l 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 pinnatitid ; involucre (purplish) 

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

 Oct. 



6. P. mainensis 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. — Perhai>s a hybrid between nos. 2 and 8. 



