34 POLYGONACE.E. Chorizanthe. 



Bracts more or less foliaceous : flowers 1^ lines long or more. 

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



undulate, unequal, oblong-ovate, acutish. 17. C. PAUKYI. 



Leaves and bracts ovate-oblong, small, tomentose beneath : 

 involucres tomentose, in diffuse cymes : flowers 2^ lines 

 long ; lobes narrow, very unequal : stamens often 6. 18. C. XANTI. 

 Leaves and oblanceolate bracts tomentose beneath : involucres 

 more glabrous, in small cymes ; teeth short : flowers 

 1^ lines long ; lobes broadly oblong : stamens 6. 19. C. WHEELEIU. 



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



unequally cleft : stamens 3 or 9. 20. C. TTNIARISTATA. 



Puberulent, thick-jointed : involucres narrow ; teeth very 



short : lobes narrow, nearly equal : stamens 3 or 6. 21. C. BREVICORNU. 

 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. 22. C. POLYGONOIDES. 

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



stoutj rigid and persistent : teeth 3, lanceolate. 23. C. RIGIDA. 



Involucres narrowly cylindrical : bracts not foliaceous. 



Leaves ovate : involucres strongly corrugated, 3-toothed. 24. C. CORRUGATA. 



Leaves narrow : involucres obscurely corrugated, 5-toothed. 25. C. WATSONI. 



1. Involucres coriaceo-chartaceous, the awns of the erect or divergent teeth not 

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

 white or pinkish: perianth 6-parted, pubescent with soft hairs, the 9 

 stamens inserted upon the base : bractlets minute. Glabrous or glandular, 

 never villous-tomentose : bracts ternate, foliaceous, more or less connate and 

 unilateral : leaves all radical and spatulate : involucres axillary and 

 terminal in open dichotomous panicles. MUCBONEA. 



* Involucres 1 3-flowered, with 3 to 6 mostly erect teeth, and with 3 to 6 divari- 



cate cuspidate or awned spurs at base: bracts small. (Centrostegia, Gray.) 



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

 usually less, branching from near the base : leaves an inch long, glabrous, slightly 

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

 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. Centrostegia Thurberi, Gray ; Benth. in DC. 

 Prodr. xiv. 27 ; Torr. & 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 the last : involucres 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 (Lobb) ; near San Bernardino, not rare, Parry. 



* * Involucres \-flowered, with 2 to 5 unequal stout divergent teeth, not spurred 



at base: bracts conspicuous. ( Mucronea, 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 inch broad : 



