GENUS 19. 



THISTLE FAMILY. 



3. Sideranthus spinulosus (Nutt.) Sweet. 



Cut-leaved Sideranthus. Sapo. 



Fig. 4210. 



Amellus spinulosus Pursh, Fl. Am. Sept. 2 : 564. 



1814. 

 Sideranthus spinulosus Sweet, Hort. Brit. 227. 



1826. 



Aplopappus spinulosus DC. Prodr. 5: 347. 1836. 

 Eriocarpum spinulosum Greene, Erythea 2: 108. 



1894. 

 S. glaberrimus Rydb. Bull. Torr. Club 27 : 621. 



1900. 



Canescent or glabrate, much branched at the 

 base, perennial by thick woody roots, 6'-i5' 

 high. Leaves pinnatifid, sessile, linear to ovate 

 in outline, i'-i*' long, \"-2\" wide, the lobes 

 with bristle-poinied teeth ; heads several or nu- 

 merous (rarely solitary), 6"-i2" broad; invo- 

 lucre hemispheric, its bracts linear, acute, ap- 

 pressed ; rays narrow ; achenes pubescent, nar- 

 rowed below; pappus soft and capillary. 



In dry soil, Minnesota and North Dakota to 

 Saskatchewan, Alberta, Colorado, Nebraska, 

 Texas and Mexico. March-Sept. 



20. STENOTUS Nutt. Trans. Am. Phil. Soc. (II) 7: 334. 1841. 



Low undershrubs, with coriaceous narrow entire evergreen leaves, scapose or leafy stems, 

 and rather large heads of both radiate and tubular yellow flowers. Involucre mostly hemi- 

 spheric, its bracts imbricated in several series, appressed, ovate to lanceolate. Receptacle 

 alveolate. Disk-flowers perfect, their corollas tubular, usually somewhat enlarged upward, 

 deeply 5-toothed. Ray-flowers fertile. Anthers obtuse at the base. Appendages of the 

 style-branches short, lanceolate. Achenes white-villous. Pappus of soft white capillary bris- 

 tles. [Greek, narrow, referring to the leaves.] 



About 1 8 species, natives of western North America. Type species: Stenotus acaulis Nutt. 



i. Stenotus armerioides Nutt. Narrow-leaved 

 Stenotus. Fig. 4211. 



Stenotus armerioides Nutt. Trans. Am. Phil. Soc. (II.) 



7: 335- 1841. 

 Aplopappus armerioides A. Gray, Syn. Fl. i : Part. 2, 



132. 1884. 



Perennial, tufted from a branched woody cauclex, 

 glabrous throughout ; flowering stems slender, naked 

 above, or quite leafless, 4'-8' high. Basal leaves nu- 

 merous, narrowly spatulate or linear, acute or acutish, 

 firm, i'-3' long, i"-2" wide, entire, narrowed below; 

 stem leaves usually 1-3, sessile, linear, sometimes 

 none; head commonly solitary, about i' broad; in- 

 volucre campanulate, 4"-6" high, its bracts broadly 

 oval, green, appressed, obtuse or retuse, scarious- 

 margined, or the inner ovate-oblong and acutish ; 

 rays 8-10 ; achenes canescent or villous ; pappus bris- 

 tles soft, white. 



In dry, mostly rocky soil, western Nebraska to Wyo- 

 ming, Utah and New Mexico. June-July. 



21. ISOPAPPUS T. & G. Fl. N. A. 2 : 239. 1841. 



Rough-hairy annual or biennial herbs, loosely paniculately branched, with alternate linear 

 to lanceolate, i-nerved, entire or somewhat toothed leaves, and small slender-peduncled heads 

 of radiate and tubular yellow flowers. Involucre campanulate-cylindric, its appressed lan- 

 ceolate or subulate bracts in 2 or 3 series. Receptacle alveolate. Ray-flowers 5-12, pistil- 

 late. Disk-flowers 10-20, perfect. Anthers not sagittate. Style-appendages narrow, hirsute. 

 Achenes terete, narrowed below, silky-villous. Pappus a single series of rough capillary 

 bristles, nearly equal in length. [Greek, equal-pappus.] 



Two known species, natives of the southern United States, the following typical. 



