226 University of California Publications in Botany. [T OL - 3 



94. TETRADYMIA DC. 



Low rigid shrubs of arid districts. Herbage clothed with 

 dense and matted or floccose wool which is deciduous in some 

 species. Leaves alternate, entire, solitary or fascicled, the prim- 

 ary ones often modified into spines. Involucre cylindric to ob- 

 long, composed of 4 to 6 firm concave overlapping bracts which 

 are often enlarged and thickened at base. Heads discoid, 4 to 9- 

 flowered. Receptacle flat, small. Corollas yellow ; lobes spread- 

 ing, longer than the short-campanulate throat, much shorter than 

 the elongated tube. Anthers exserted, sagittate at base, the tips 

 triangular-lanceolate. Style-branches flat, obtuse. Achenes 

 terete, faintly 5-nerved. Pappus of fine and soft scabrous capil- 

 lary bristles, white or whitish. 



Pappus copious, much exceeding the hairs of the achene, or the achenes 



glabrous. 

 Heads 4-flowered: leaves not spiny. 



Leaves linear to oblanceolate, 1 to 2 cm. long, not glabrate 



1. T. canescens. 



Leaves linear to subulate, less than 1 cm. long, glabrate 



2. T. glabrata. 



Heads 5-flowered: upper leaves rigid, spiny 3. T. stenolepis. 



Pappus-bristles in a single series, scarcely exceeding the long ascending 

 hairs of the achene. 



Heads pedunculate, scattered or loosely racemose 4. T. spinosa. 



Heads nearly sessile in a close terminal cyme ..5. T. comosa. 



1. T. canescens DC., Prodr. v. 440 (1837). 



Stems 1 to 3 dm. high, freely branching: foliage and in- 

 florescence white with a permanent close tomentum : leaves some- 

 what crowded but rarely at all fascicled, linear or linear-lanceol- 

 ate, pungently acute, mostly 1 to 2 cm. long : heads short-pedunc- 

 ulate in cymose clusters terminating the short branchlets: in- 

 volucre 8 to 10 mm. high, 4-flowered; bracts 4 or 5, strongly 

 carinate, oblong : achenes varying from glabrous to villous : 

 pappus copious, sordid or yellowish. 



Upper Sonoran and Transition zones below 2300 m. alt: San 

 Bernardino Mts. (Barton Flat, South Fork, Bear Valley, Doble). 

 San Antonio Mts. (Rock Creek), Sierra Nevada and Rocky Mts. 

 Also (in the var. inermis (Nutt) Gray, with shorter leaves and 



