34 POLYGON ACE.E. ChorizanfTit 



Bracts more or less foliaceous : flowers li lines long or more. 

 Leaves narrow, not toineniose : teeth long-divergent : lobes 



UTidulate, une(jual, oblong-ovate, acutish. 17. C. Pauuyi. 



Leaves anil bracts ovate-oblong, small, tonientose beneath : 

 involucres tomentose, in diffiise cymes : flowers 2^ lines 

 long ; lobes narrow, very une(iuai ; stamens often 6. 18. C. Xaxti. 

 Leaves and oblanceolate bracts toniento.se lieneath : involucres 

 more glabrous, in small cymes ; teeth short : flowers 

 li lines long ; lobes broadly oblong : stamens 6. 

 Villous-pubescent : one tooth long-awned : flowers yellow, 



unc([ually cleft : stamens 3 or 9. 

 Puberulent, thick-jointed : involucres narrow ; teeth very 

 short : lobes narrow, nearly equal : stamens 3 or 6. 

 Villous-pubescent: bracts distinct : involucres 3-5-toothed, 1-flowered : 

 flowers 6-cleft : stamens 6 or 9, on the throat. 

 Involucres broadly triangular : bracts foliaceous. 



Leaves and bracts narrow ; floral bracts very short : teeth broad. 

 Leaves and bracts ovate, tomentose beneath : floral bracts elongated, 

 stout, rigid and jiersistent : teeth 3, lanceolate. 

 Involucres narrowly cylindrical : bracts not foliaceous. 

 Leaves ovate : involucres strongly corrugated, 3-toothed. 

 Leaves narrow : involucres obscurely corrugated, 5-toothed. 



§ 1. Involucres corincen-cliartaceous, the awns of the erect or divergent teeth not 

 uncinate : Jtoicers on slender pedicels, included or more or less exserted, 

 ivhite or pinldsh : 'perianth Q>-paHed, pidiescent with soft hairs, the 9 

 staviens inserted upon the base : hractlets mimcte. Glabrous or fjlandidar, 

 never villous-tomentose : bracts tern ate, foliaceous, moi^e or less connate and 

 unilateral : leaves cdl radical and spattdate : involucres axillary and 

 terminal in open dichotomous jjanicles. — Mucronea. 



* Involucres 1 - o-floivered, with 3 to & mostly erect teeth, and with 3 f o 6 divari- 



cate cuspidate or aivned spurs at base: bracts small. — {Centrosteyia, Gray.) 



1. C. Thurberi, Watson. More or less gkndular-puberulent, 6 inches high or 

 iLsually lrs8, Itnincliiny from near the base: leaves an inch long, glabrous, slightly 

 ciliate: bracts oblong, more or less united, 1 to 3 lines long: involucres glabrovis, 

 chartaceous, triangular-prismatic, obscurely reticulated, 2 or 3 lines long and | to 1 

 line broad, with 3 broad straight-awned spurs at base, and with 3 to 5 broad and 

 short erect teeth : flowers 1 or 2, rarely exserted, nearly a line long, pubescent at 

 base : segments oblong-spatulate, obtuse or emarginate, the alternate ones slightly 

 shorter. — Proc. Am. Acad. xii. 269. Centrosteyia Thurberi, Gray ; Benth. in DC. 

 Prodr. xiv. 27 ; Torr. Sc Gray, 1. c. 192. 



In the desert region of S. California and eastward, from Fort Tejon {Rothrock), San Bernardino 

 {Parry) and San Felipe (Thurber) to Southern Utah. 



2. C. leptoceras, Watson, 1. c. Very slender, nearly glabrous : leaves and bracts 

 as in tlie List : iiivdlucres 2 or 3 lines long, somewhat hirsute, deeply 4 -6-cleft, the 

 coriaceous turbinate base surrounded by as many rigid usually uncinate awn-like 

 spurs ; lobes rigid, narrow, unequal, attenuate into straight rigid somewhat divergent 

 awns : flowers 2 or 3, occasionally exserted, villous-pubescent, half a line long : 

 segments narrowly oblong to ovate, nearly equal. — Centrostegia leptoceras, Gray ; 

 Torr. & Gray, 1. c. 



Plains of San Gabriel (Lohh) ; near San Bernardino, not lare, Pnrry. 



* * Involucres 1-flovered, with 2 to 5 unerpial stout divergent teeth, not spurred 



at base: Irracts conspicuous. — (§ Miuronea, Torr. & Gray.) 



3. C. perfoliata, Gray. Sparingly hirsute and glandular, a foot high or less, 

 often bright red : leaves an inch or two long : bracts connate about the stem, form- 

 ing a somewhat unilateral triangular reticulated disk, the lower often an incli broad : 



