Tetradymia. COMPOSITiE. 379 



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

 and by Brewer. 



1 89. TETRADYMIA, DC. (TerpaSu/i-os, four together, the heads of the 

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

 of N. America), sometimes spinescent, canescently 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. GO ; Torr. & Gray, Fl. ii. 447. 



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

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

 in the same species : undershrubs, a foot or two high. 



T. canescens, DC. Permanently canescent with a dense close tomentum, 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 tlieni short-pedunculate. — Prodr. 1. c. ; Deless. 

 Ic. iv. t. 60. — Hills and plains, along with Artemisia irideiitatn, N. Wyoming and Brit. 

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



Var. inermis, Gray, Bot. Calif, i. 408. A form witli 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 

 onl\' form eastward. 



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

 branches more slender, spreading : leaves at length naked and green, ])rimary ones slender- 

 subulate, cuspidate, on yt)ung slioots appressed, half-inch long ; tliose of fascicles in their 

 axils spatulate-linear, fleshy, pointless : heads mostly short-pedunculate : involucre often 

 glabrate: akenes as far as known very villous. — Pacif. R. 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 Beckicilh. 



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. e. T. spiiwsa, Nutt. 1. c, not Hook. 

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



§ 2. LagotiiXmnus, 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. — Lagothamrms, Nutt. Trans. 

 Am. Phil. Soc. vii. 416. 



T. spinosa, Hook. & Arn. Branches divaricate, rigid, bearing rigid an<l straight or re- 

 curved spines in place of primary leaves : secondary leaves fascicled in tiieir a.\ils, small, 

 flesliy, liuear-clavate, glabrous or glabrate : heads scattered, pedimculate, fully lialf-inch 

 long : pai^pus of comparatively rigid capillary bristles, somewliat surpassing the wool of the 

 akene. — Bot. Beech. 360; 'I'orr. & Gray, 1. c. ; Gray, Bot. Calif. 1. c. — La<iothamnus micro- 

 phi/IJiis & L. ambif/uus, 'Nntt. Trans. Am. Phil. Soc. vii. 416. — S. Wyoming and Utah to 

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



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

 tose ; the earlier 2 or 3 inches long and 2 lines wide, plane ; those of tlie branches often fili- 

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

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

 the summit of the branches : pappus finer and more scanty, 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, Parry, Lemmon, Parish, 

 Cleveland. 



