CAKDUACEAE 1205 



1. Thurovia triflora Rose. Stems 2-4.5 dm. tall, slender, with straggling or bushy 

 branches : leaves few ; blades linear, 6-18 mm. long, acute, entire : involucres about 3 

 mm. high, 3-flowered ; bracts few, the outer with green linear acute tips : corolla-lobes 

 spreading : achenes turbinate, 1 mm. long : pappus-scales 2 mm. long, the base oblong, 

 the tips slender, shorter than the bases, sometimes barbed. 



On prairies, Texas. Fall. 



46. CHAETOFAFFA DC. 



Annual or biennial very slender caulescent herbs. Leaves alternate : blades entire, 

 ciliate or spinulose-serrulate. Heads small, radiate. Involucres narrow : bracts in few 

 series, acute or acuminate. Receptacle flat, naked. Ray-flowers in 1 row, pistillate. 

 Disk-flowers perfect or the central staminate. Anthers obtuse and entire at the base. 

 Stigmas with narrow obtuse appendages. Achenes nearly terete, 5-ribbed, sometimes nar- 

 rowed at both ends. Pappus of 5 or more scales alternating with 5 scabrous bristles. 



Involucres 4 mm. high : achenes pubescent : pappus-scales narrowly oblong. 1. C. asteroidu. 



Involucres 6 mm. high : achenes glabrous or nearly so ; pappus-scales cuneate. 2. C. Parryi, 



1. Chaetopappa aateroides (Nutt. ) DC. Stems slender, 0.5-3 dm. tall, minutely 

 pubescent, more or less diffusely branched. Leaf-blades spatulate to linear, 0.5-2 cm. long, 

 the lower ones slender-petioled : involucres 4 mm. high, oblong or oblong-turbinate ; bracts 

 linear, glabrous, scarious-margined, spreading in age : ray-flowers 5-12 ; ligules narrowly 

 oblong, 2-3 mm. long : achenes 1.5 mm. long : pappus-scales oblong, hyaline. 



In dry soil. Missouri to Texas. Spring and summer. A form without pappus-awns In any flow- 

 ers and the pappus-scales crown-like, is C. asteroides imb&rbu A. Gray. Eastern Texas. 



2. Chaetopappa Parryi A. Gray. Stems 1-2 dm. tall, nearly glabrous, corymbose 

 above, the branches wiry, leaf-blades somewhat leathery, spatulate to linear-oblanceolate. 

 1-2 cm. long, acutish or apiculate, ciliate : involucres cylindric, 6 mm. high ; bracts linear- 

 lanceolate to linear, acute, with broad scarious margins : ray-flowers 6-7, with oblong lig- 

 ules : achenes 2.5 mm. long, glabrous or nearly so : pappus-scales cuneate, 4-5. 



In dry soil, Texas. Spring and summer. 



47. DISTASIS DC. 



Annual relatively low caulescent herbs, with pubescent foliage. Leaves alternate : 

 blades entire or sparingly toothed. Heads small, radiate, peduncled. Involucres hemi- 

 spheric or campanulate, many-flowered : bracts scarious-margined, in few series. Receptacle 

 flat, slightly pitted. Ray-flowers pistillate, in about 1 series. Disk-flowers perfect, fruit- 

 producing. Anthers obtuse and entire at the base. Style-branches flattened, with narrow 

 appendages. Achenes flattened, with slightly margined nerves. Pappus a series of hyaline 

 scales alternating with as many bristles. 



1. Dlstasis modsta DC. Stems commonly branched at the base, 0.5-3 dm. tall, 

 hirsute and strigillose. Leaf- blades spatulate to linear, 0.5-1.5 cm. long, acute or acutish : 

 involucres 3 mm. high, hemispheric ; bracts linear, acute or acuminate, often sparingly 

 pubescent : achenes 2 mm. long, pubescent : pappus-scales 5, truncate or eroded at the 

 apex, alternating with 5 bristles. 



In dry soil, Texas and adjacent Mexico. 



48. TOWNSENDIA Hook. 



Tufted scapose or caulescent herbs, often with caudex-like stems or branches. Leaves 

 alternate : blades narrow, often crowded and broadest above the middle, entire. Heads 

 relatively large, showy, sessile or peduncled. Involucres campanulate to hemispheric : 

 bracts herbaceous, in several series. Receptacle nearly flat. Ray-flowers pistillate, with 

 white or pink ligules. Disk-flowers mostly perfect. Anthers obtuse and entire at the base. 

 Stigmas flattened, each with a lanceolate or narrow appendaged. Achenes various, those 

 of the ray mostly 3-angled, those of the disk flattened. Pappus a single series of firm 

 bristles or scales. 



1. Townsendia Wilcoxiana Wood. Depressed, tufted. Leaves several or numer- 

 ous, crowded on the short caudex-like stems ; blades linear-spa tulate, 2-4.5 cm. long, spar- 

 ingly pubescent : heads sessile : involucres about 1 cm. high ; bracts lanceolate to linear- 

 lanceolate, the inner 11-13 mm. long, like the outer ciliate and often magenta-tipped : ray- 

 flowers numerous, with narrow ligules 1-1.5 cm. long. 



In dry soil, Colorado to the Indian Territory and Arizona. Spring and summer. 



