50 DAVKNPOKT ACADKMV OF NATURAL SCTKNCF.S. 



CHORIZANTHE, R. Br. 



Involucres tubular or infundibuliform, sessile, 2-6 angled or costate, 

 and 2-6 toothed or cleft, the divisions more or less divaricate, and 

 terminating in cusps or rigid awns, frequently uncinate. Flowers 1-3, 

 pedicellate or nearly sessile, without l)racteoles, included in the involu- 

 cre, or more or less exsert, rarely obsolete; perianth 6 parted or cleft; 

 stamens 9, rarely 3-6, inserted on the base, or more or less adnate to 

 the tube, rarely on the throat of the perianth. Styles linear, stigmas 

 capitate. Ovary glabrous; akene broadly or narrowly triangular, 

 beaked. Embryo with inflexed or straight radicle. 



Dichotomously branched plants, with rosulate radical leaves and 

 jointed stems, cauline bracts opposite or unilateral, trifid or simple, 

 rarely verticillate, usually awn-pointed. — Benth. & Hook., Gen. PI., 

 TIL, p. 93. Watson, Bot. Cal., II. Laslarricea, Remy. 



Synoptical Arrangement of Species. 



(Excliulintf South AniLTiean FerunniuLs.) 



Group A. Campylosperma. 

 Cotyledons orbicular^ acciimbent to the inflexed radicle. 

 §1. Centrostegia. Involucres 2-3 flowered, flowers pedicellate, 

 the secondary or tertiary flowers often imperfectly developed. Stamens 

 9, inserted on the base of the perianth. 



* Involucres unequally 5-6 cleft or parted, saccate near the base of the tube 

 with 3-6 divaricate spurs, straight av*'ned or uncinate; usually 2 developed flowers; 

 involucral bracts unilateral, trifid and cuspidate. Centrostegia Torr. & Gray. 



I. C. Thurkeri, Watson, 1. c. t^rect, smooth or glandular-pubes- 

 cent, with slender dichotomous branches above the short (1-4 inches) 

 caudex; radical leaves oblong-spathulate, sessile, smooth, with ciliate 

 hairs on the margins; cauline bracts short, trifid, accuminate ; involu- 

 cres scattered, single, chartaceous, reticulated; teeth 5, short, triangular, 

 slightly unecjual, cuspidate; tube protuberant below into 3 (rarely 4) 

 saccate, divaricate, cuspidate spurs; flowers usually 2 (with occasional 

 traces of a third, undeveloped), une([ually pedicelled, the longer exsert; 

 perianth deeply parted, slightly une(]ual, hispid hairy externally; sta- 

 mens 9; styles as long as the ovary; akene triangiflar, beaked; embryo 

 with slender inflexed radicle. 



Habitat : Eastern desert districts of the Mojave, and Colorado val- 

 ley, to Southern Utah. Figured in Pacific R. R. Rep., Vol. IV., pi. 8. 



