Genus 6S.] 



THISTLE FAMILY. 



441 



68. THELESPERMA Less. Linnaea, 6: 511. 1831. 



Glabrous annual or perennial herbs, with opposite linear and undivided, or fineU dissec- 

 ted leaves, and long-peduncled heads of both tubular and radiate flowers, or the rays want- 

 ing. Involucre hemispheric or campanulate, of 2 distinct series of bracts, the outer short, 

 narrow and somewhat spreading, the inner united nearly to or beyond the middle into a cup, 

 their tips scarious-margined. Receptacle flat, chaffy, the 2-nerved broad white scarious chaff 

 subtending the disk-flowers and achenes: Ray-flowers, when present, neutral, the rays yel- 

 low, entire or toothed. Disk-flowers perfect, fertile, their corolla with a slender tube and 

 5-toothed limb. Anthers obtuse and entire at the base. Style-tips acute. Achenes, some or 

 all of them, papillose on the back, oblong or linear, slightly compressed or terete, wingless. 

 Pappus of 2 retrorsely hispid awns or scales, or sometimes none. [Greek, nipple-seed.] 



About 7 species, natives of the south central United States, Mexico and southern South America. 



Rays large; pappus-awns shorter than the width of the achene. 



Leaves not rigid, their segments filiform-linear; annual or biennial. i. T. ambiguum. 



Leaves rigid, their segments linear; perennial. 2. T. trifidum. 



Rays inconspicuous, or none; awns longer than the width of the achene. 3. T. gracile. 



i. Thelesperma trifidum (Poir. ) Britton 



(Fig- 395i ) 



Coreopsis trifida Poir. in Suppl. Lam. Lncycl. 



2:353. 1811. 

 Thelesperma fill 'folium A. Gray, Kew Journ. 



Bot. 1: 252. 1849. 

 Thelesperma trifidum Britton, Trans. N. Y. 



Acad. Sci. 9: 182. 1890. 



Annual or biennial; stem branched, i-3 

 high. Leaves numerous, not rigid, \%'-i r 

 long, bipinnately divided into filiform or 

 linear-filiform segments; heads several or 

 numerous, I2 // -i5 // broad; outer bracts of 

 the involucre about 8, subulate-linear, equal- 

 ling or more than half as long as the inner, 

 which are united not higher that the middle; 

 rays 6-10, somewhat spatulate, 3-lobed; disk 

 purple or brown; achenes linear-oblong, 

 straight, or slightly curved, the outer ones 

 strongly papillose; awns of the pappus not 

 longer than the width of the summit of the 

 achene. 



In dry soil, Nebraska to Texas. June-Aug. 



Fine-leaved Thelesperma. 



2. Thelesperma ambiguum 



A. Gray. Stiff Thelesperma. 



(Fig. 3952.) 



Thelesperma ambiguum A. Gray, Proc. Am. 

 Acad. 19: 16. 1S83. 



Perennial from a deep woody root and 

 slender rootstocks; stem rigid, usually much 

 branched, i-i)4 high. Leaves usually 

 numerous, i>^ / -2 / long, bipinnately divided 

 into entire rigid linear segments, but less 

 compound than those of the preceding spe- 

 cies; outer bracts of the involucre lanceolate- 

 subulate, usually much shorter than the 

 inner ones, which are united to about the 

 middle; rays (rarely wanting) and achenes 

 similar to those of the preceding. 



In dry soil, Montana, Colorado and Nebraska 

 to Texas and New Mexico. June-Aug. 



