Genus 27.] 



THISTLE FAMILY. 



351 



Silk\- or Low Townsendia. 



2. Townsendia exscapa (Richards) Porter 



(Fig. 3726.) 



Asler (?) exscaptis Richards. App. Frank. Joum. •52. 



1823. 

 Totfiiseitdta sertcea Hook. Fl. Bor. .Km. 2: 16. pi. //91. 



1834- 

 Toutisendia exscapa Porter, Mem. Torr. Club, 5: 321. 



Acaulescent, or nearly so, from a deep woody 

 root, tufted, I'-j' high. Leaves all clustered at 

 the base, narrowly linear or slightly spatulate, i'-i' 

 long, \"-2\'z" wide; heads closely sessile, I'-i^' 

 broad, equalled or surpassed by the leaves; invo- 

 lucre broadly campanulate, its bracts lanceolate, 

 acute, the inner scarious -margined; rays white or 

 purplish; pappus of both ray and disk-flowers a 

 row of rigid bristles, those of the rays shorter and 

 smaller. 



In drj' soil, Northwest Territory to Nebraska, .\rizona 

 and New Mexico. Often silky-pubescent. April-July. 



28. CHAETOPAPPA DC. Prodr. 5: 301. 

 Annual slender much branched herbs.'.with small alternate entire leaves, and small long- 

 pcduncled heads of both tubular and radiate flowers. Involucre narrowly campanulate, its 

 bracts lanceolate, acute or acuminate, imbricated in few series, the outer slightly shorter. 

 Receptacle small, naked. Ray-flowers in i row, pistillate. Disk-flowers perfect, or the cen- 

 tral ones staminate, their corollas 5-lobed. Anthers obtuse and entire at the base. Style- 

 branches narrow, flattened, their appendages short, obtuse. Achenes nearly terete, fusiform, 

 or linear, 5-ribbed. Pappus usually of 5 rigid awn-like scabrous bristles, alternating with 

 as many short scales or more. [Greek, bristle-pappus.] 



Two known species, natives of the southwestern United States, The genus Dislasis DC. ( Cltae- 

 lopappa inndfsla -A. Gray), is here regarded as distinct. 



I. Chaetopappa asteroides DC. 



Chaetopappa. (Fig. 3727.) 



Chaetopappa asteroides DC. Prodr. 5: 301. 1S36. 



Annual, pubescent, erect,2'-i2'high, the branches 

 filiform. Lower and basal leaves spatulate, ob- 

 tuse, Yi'-i' long, petioled, the upper linear, much 

 smaller and bract-like, sesgile; heads about 3" broad; 

 involucre about 2" high, its bracts scarious-margincd, 

 glabrous or nearly so; rays 5-12, raised on slender 

 tubes; central sterile flowers usually awnless; shorter 

 scales of the pappus of the fertile flowers hyaline, 

 sometimes lacerate. 



In drj' soil, Missouri to Texas and northern Mexico. 

 April-July. 



29. BOLTONIA L'Her. Sert. Angl. 27. 1788. 



Perennial glabrous branching herbs, with striate or angled stems, alternate entire sessile 

 or clasping leaves, and numerous rather large heads of both tubular and radiate flowers, 

 paniculate, or solitary at the ends of the branches. Involucre hemispheric or broadly cam- 

 panulate, its bracts scarious- margined, imbricated in few series, the outer slightly shorter. 

 Receptacle convex or conic, foveolate. Ray-flowers pistillate. Disk-flowers perfect, their 

 corollas elongated, 5-lobed. Anthers obtuse and entire at the base. Style-branches flattened, 

 their appendages short, lanceolate. Achenes flattened, obovate, their margins thickened or 

 narrowly winged, glabrous or nearly so. Pappus a series of short scales, usually with 2-4 

 slender rigid bristles. [Named for James Bolton, an English botanist of the iSth century.] 



As here limited, the genus consists of the 4 following species, with perhaps a fifth in Oregon. 



