592 COMPOSITAE (COMPOSITE FAMILY) 



branches not striate: radical leaves spatulate or oblong, from nearly entire 

 to runcinate-pinnatifid ; the cauline small and entire, soon reduced to minute 

 bracts: involucre oblong, 4 mm. high, 4-5-flowered, of as many bracts and 

 1 or 2 very small calyculate ones: achenes 2-3 mm. long, gradually tapering 

 from the truncate summit to base, broadly 4-5-costate, or rather narrowly 

 4-5-sulcate, somewhat longer than the bright white pappus. (Lygodesmia 

 exigua Gray.) Southern Colorado through the desert areas to California. 



101. PRENANTHES Vaill. RATTLESNAKE ROOT 



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, the principal bracts in 1 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 10-ribbed. Pappus 

 of copious, rather rigid, simple, white, or reddish-brown bristles. 



Basal leaves obovate . . . . . . . . . . 1. P. racemosa. 



Basal leaves triangular-sagittate 2. P. sagittata. 



1. Prenanthes racemosa Michx. Fl. Bor. Am. 2: 83. 1803. Stems simple, 

 3-12 dm. high, leafy up to the inflorescence, with the leaves glabrous and 

 glaucous: leaves ordinarily only denticulate; radical and lower leaves spatulate- 

 oblong to obovate, tapering into winged petioles; the upper cauline lanceolate 

 to ovate^ partly clasping the broader ones by a cordate or auriculate base: 

 heads not at all drooping, crowded in an elongated thyrsus, 1-5 dm. long; 

 involucre loosely hirsute: flowers purplish: achenes about 15-nerved, some- 

 what angled by 4 or 5 of the stronger nerves. Nabalus racemosus DC. From 

 Colorado to the Saskatchewan, thence eastward across the continent. 



2. Prenanthes sagittata (Gray) A. Nels. Glabrous or nearly so, 2-5 dm. 

 high, the larger plants branching: leaves sagittate or hastate, with basal lobes 

 mostly slender and prolonged : heads in a virgate panicle ; involucre pale green, 

 very glabrous: achenes slender, about 6 mm. long, usually tapering a little 

 upwards. P. alata sagittata. (Nabalus sagittatus Rydb. Mem. N. Y. Bot. 

 Gard. 1: 463. 1900.) Montana and Idaho and probably in Wyoming. 



102. CREPIS L. 



Perennial or annual herbs, with alternate or all radical mostly toothed or 



Einnatifid leaves and small or middle-sized heads of yellow flowers. Involucre 

 jw- to many-flowered, cylindric, campanulate, or swollen at base, the princi- 

 pal bracts in one series, equal, with a number of exterior small ones. Re- 

 ceptacle mostly flat, naked or short-fimbrillate. Achenes columnar to fusi- 

 form, 10-20-ribbed or -nerved, not transversely rugose, narrowed at the base 

 and apex. Pappus of copious white and usually soft capillary bristles. 



Achenes dilated or discoid at the insertion of the pappus; low glaucous 



plants, with entire or merely repand leaves. 



From running rootstocks; leaves mainly radical . . . 1. C. nana. 



From a taproot; leaves mainly cauline ...... 2. C. elegans. 



Achenes not dilated or discoid at the insertion of the pappus; leaves 



usually more or less laciniate-pinnatifid, rarely entire. 

 Herbage green, glabrous or sometimes slightly hirsute, never white- 

 pubescent or scurfy. 

 Leaves usually somewhat glaucous; the involucre glabrous or 



only puberulent when young . . . " " . . . 3. C. glauca. 

 Leaves not glaucous, glabrous or often somewhat pubescent or 



hirsute; involucre pubescent to glandular-hispidulous. 

 Involucre pubescent or hirsute . . ' . . . . . 4. C. runcinata. 



Involucre glandular-hispid . . . . . . 5. 'C. riparia. 



Herbage minutely white-pubescent or scurfy. 



Involucres glabrous, 5-7-flowered . . , . . 6. C. acuminata. 



