THISTLE FAMILY 859 



cm. long, 1-3 mm. wide; inflorescence fastigiate-cymose; bracts oblong, rounded 

 at the apex, all but the innermost with a thickened greenish tip; achenes glabrous 

 or slightly puberulent. C. Bakeri Greene. Mountains,: Wyo. Colo. Utah. 

 Submont. Jl-S. 



42. C. turbinatus (M. E. Jones) Rydb. Shrub, about 1 m. high, bushy; 

 leaves long and narrow, canaliculate, the uppermost much reduced, glabrous, or 

 slightly viscid in the inflorescence; bracts 5 or 6 in each vertical row, the lowest 

 minute, all obtuse, merely apiculate, with a darker center, the inner oblong to 

 linear, 8 mm. long. B. turbinata M. E. Jones. Gravel: Utah. Son. S. 



16. ISOCOMA Greene. 



Herbaceous or shrubby plants, usually with viscid foliage. Leaves alternate, 

 entire, toothed, or pinnately parted. Heads discoid. Involucres mostly cam- 

 panulate, several- to many-flowered; bracts leathery, obtuse or acutish, well 

 imbricate, with more or less thickened tips. Disk-flowers perfect; corolla yellow, 

 the throat much inflated. Tips of the style-branches subulate, lanceolate or 

 broader. Achenes short, broadened upwards, usually silky-strigose. Pappus of 

 numerous barbellate bristles. 



Bracts acute, linear-lanceolate. 1. /. pluriflora. 



Bracts obtuse or obtusish, linear, oblong, or oblanceolate. 

 Leaves 1-ribbed, the lower often toothed. 



Plant herbaceous, except the suffruticose base; bracts comparatively thin. 



2. I. Wrightii. 



Plant shrubby; bracts much thickened, especially at the apex. 3. /. acradenia. 

 Leaves triple-nerved, entire. 4. /. scopulorum. 



1. I. pluriflora (T. & G.) Greene. Suffrutescent; stems angular, glabrous; 

 leaves narrowly linear, obscurely 1-nerved, 3-6 cm. long; heads 8 mm. high, 5 

 mm. broad, 15-18-flowered, crowded at the ends of the branches in a fasciculate 

 corymb; bracts smooth, shining, not thickened at the apex. Bigelovia pluriflora 

 A. Gray. Plains: Colo. Son. 



2. I. Wrightii (A. Gray) Rydb. Stems 3-6 dm. high, strict, glabrous; 

 eaves thickish, narrowly linear, entire, or the lower toothed, somewhat scabrous; 



heads 5-6 mm. high, 4-5 mm. broad, 7-15-flowered, numerous in a large corym- 

 biform cyme; bracts oblong or broadly lanceolate, obtuse. Linosyris Wrightii 

 A. Gray. B. Wrightii A. Gray. Banks and saline soil: Tex. Colo. Utah 

 Ariz.; n Mex. Son. Au-S. 



3. I. acradenia Greene. Low shrub, 3-6 dm. high, much branched, gla- 

 brous and glutinous; leaves narrowly oblanceolate, entire, 2-4 cm. long; heads 

 6-8 mm. high, 6-10-flowered, corymbose-clustered; bracts oblong, obtuse, with 

 a conspicuous gland; achenes strigose. Desert regions: s Calif. s Utah Ariz. 

 L. Son. S-O. 



4. I. scopulorum (M. E. Jones) Rydb. Low shrub, about 5 dm. high, with 

 straw-colored branches; leaves linear, 2-7 cm. long, acute, finely puberulent or 

 glabrate, scabrous on the entire margins; heads few, corymbose; involucres tur- 

 binate, nearly 1 cm. high; bracts well imbricate in 6-7 series, elliptic to oblong, 

 yellowish, with a green spot on the back; achenes hispid. B. Menziesii scopulorum 

 M. E. Jones. Hesperodoria scopulorum Greene. Canons: s Utah. Son. Sub- 

 mont. Au-S. 



16. PRIONOPSIS Nutt. 



Annual or biennial, caulescent glabrous herbs. Leaves alternate, sessile, 

 spinulose-toothed. Heads radiate, showy. Involucres broadly hemispheric; 

 bracts well imbricate in several series, the outer spreading; receptacle naked. 

 Ray-flowers numerous, pistillate; ligules yellow. Disk-flowers numerous, per- 

 fect; corolla yellow. Anthers obtuse at the base. Style-branches with linear- 

 lanceolate appendages. Achenes glabrous, those of the rays broader. Pappus 

 of few firm, hair-like bristles, the outer often shorter; all deciduous. 



1. P. ciliata Nutt. Stem 8-15 dm. high, sparingly branched, glabrous; 

 leaves numerous, oval, ovate, or oblong, saliently dentate, with spinulose-tipped 

 teeth; heads few, corymbose; involucres about 1 cm. high, 2-2.5 cm. broad; bracts 



