Tetradymia. COMPOSIT/E. 379 



hills and arid plains, from Los Angeles Co., California, to Arizona ; first coll. by Heermann 

 and by Brewer. 



1 89. TETRADYMIA, DC. (TerpaSu/xos, four together, the heads of the 

 principal species only 4-flowered.) — Low and rigid shrubs (of the arid interior 

 of N. America), sometimes spinescent, canescentlj tomentose ; with alternate and 

 sometimes fascicled narrow and entire leaves, rather large cymose or clustered 

 heads of yellow flowers, and a copious white pappus. — Prodr. vi. 540; Deless. 

 Ic. Sel. iv. t. 60 ; Torr. & Gray, Fl. ii. 447. 



§ 1. EuTETRADtJiiA. Involucre 4-flowered, of 4 or 5 bracts: pappus ex- 

 tremely copious : akenes eitlier very villous, glabrate, or glabrous, varying even 

 in the same si^ecies : undershrubs, a foot or two high. 



T. canescens, r)C. Permanently canescent with a dense close tomeutum, unarmed, fas- 

 tigiately branched : leaves from narrowly linear to spatulate-lanceolate, an inch or less long : 

 heads half to three-fourths inch long, most of them short-pedunculate. — Prodr. 1. c. ; Deless. 

 Ic. iv. t. 60. — Mills and plains, along with Artemisia rridentata, N.Wyoming and Erit. 

 Columbia to New Mexico, Arizona, and eastern borders of California. Passes freely into 



Var. inermis, Gray, Bot. Calif, i. 408. A form with shorter and crowded brandies, 

 shorter leaves more inclined to spatulate and lanceolate, and smaller heads. — T. inermis, 

 Nutt. Trans. Am. Phil. Soc. vii. 415; Torr. & Gray, 1. c. — The commonest and almost the 

 only form eastward. 



T. glabrata, Gray. Whitened with looser at length deciduous tomeutum, unarmed : 

 branches more slender, spreading: leaves at length naked and gi-een, primary oues slender- 

 suljulate, cuspidate, on j'oung shoots appressed, half-inch long; those of fascicles in their 

 axils spatnlate-linear, fleshy, pointless : heads mostly short-pedunculate : iuvolucre often 

 glalirate: akenes as far as known very villous. — Pacif. 11. Pep. ii. 122, t. 5; Eaton, Bot. 

 King Exp. 193 ; Gray, Bot. Calif, i. 408. — Common in Utah and to the eastern borders of 

 California and S. E. Oregon ; first coll. by Beckwilh. 



T. Nuttallii, Torr. & Gray. Pubescence and foliage of T. canescens, var. inermis, bearing 

 rigid divergent spines in place of primary leaves ; leaves of the axillary fascicles mostly 

 spatulate : heads more glomerate. — Fl. 1. c. ; Eaton, 1. c. T. spinosa, Nutt. 1. c, not Hook. 

 & Arn. — Utah and Wyoming or S. Idaho, Nuttall, Watson. 



§ 2. Lagotii^mnus, Torr. & Gray, 1. c. Involucre 5-9-flowered, of 5 or 6 

 broader bracts : proper pappus less copious, reduced nearly or quite to a single 

 series of bristles, which are covered 'by a false pappus of the extremely long very 

 soft and white woolly hairs which densely clothe the akene : shrubs 2 to 4 feet 

 high, at least the branches densely white-tomentose. — Lagothamnus, Nutt. Trans. 

 Am. Phil. Soc. vii. 416. 



T. spinosa, Hook. & Arx. Branches divaricate, rigid, bearing rigid and straight or re- 

 curved spines in place of primary leaves : secondary leaves fascicled in their axils, small, 

 fleshy, liuear-clavate, glabrous or glabrate : heads scattered, pedunculate, fully half-inch 

 long : pappus of comparatively rigid capillary bristles, somewhat surpassing the wool of the 

 akene. — Bot. Beech. 360; Torr. & Gray, 1. c. ; Gray, Bot. Calif. 1. c. — Lacjothamnus micro- 

 phijllus & L. ambicjiius, "Sutt. Trans. Am. Phil. Soc. vii. 416. — S. Wyoming and Utah to 

 Idaho, E. Oregon, and along tlie southeastern borders of California to border of Arizona. 



T. COmosa, Gray. Branches erect, elongated : primary leaves linear, soft, floccose-tomen- 

 tose ; the earlier 2 or 3 inches long and 2 lines wide, ])lane ; those of the branches often fili- 

 form and deciduous, some of the upper changed to long and soft spines ; fascicled secondary 

 leaves wanting, or fewer and like tliose of T. spinosa: heads corymbose or glomerate at 

 the summit of the branches : pappus finer and more scant}', concealed by the long wool of 

 the akene. — Proc. Am. Acad. xii. 60; Bot. Calif, ii. 458. — N. W. borders of Nevada 

 (Lemmon), San Bernardino and San Diego Counties, California, Parrij, Lcnimon, Parish, 

 Cleveland. 



