BUCKWHEAT FAMILY 



399 



Fig. 70. a, CHORIZANTHE LEPTOCERAS Wats.; 

 involucre. &, C. THTJRBERI Wats. ; involucre, 

 x 6. 



and 3-horned; teeth erect, tipped 

 with a short straight spine; horns 

 near base saccate, spreading, short, 

 thick, each tipped with a short 

 straight spine; flowers pedicelled; 

 calyx deeply parted, hairy on the 

 outside ; stamens 9 or 6. 



Arid valleys, Colorado and 

 Mohave deserts north to Inyo 

 Co. ; southerly Sierra Nevada and 

 San Carlos Range. S. Nevada, 

 Arizona. 



A singular species remarkable for its 

 saccate spurs. The spurs do not diverge 

 symmetrically but 2 of them stand almost 

 opposite with the third spur equidistant between them on one side. The side of the involucre 

 opposite the third spur is therefore somewhat flattish (Helen Gilkey) and the single-toothed 

 lobe of the tube (with its single nerve) stands over the interval between the nearly opposite 

 spurs, whereas double-toothed lobes and double nerves correspond to the other intervals. This 

 species is the type of Gray 's Centrostegia, which by reason of its saccate spurs, peculiar in- 

 volucral teeth and parted calyx, has some claims to consideration as a monotypic genus. 



Locs. Jacumba, D. Cleveland; San Felipe, T. Brandegee; Cuyamaca, K. Brandegee; 

 Coyote Canon, Jepson 1432a; Lancaster, Hall $ Chandler 7387; Victor, Jepson 5617; Kramer, 

 Jepson 5341; Mt. Pinos, Hall 6349; Tehachapi Pass, StoTces ; Kernville, T. Brandegee; inner 

 South Coast Eange at Alcalde (ace. Zoe, 4: 158); Panamint Mts., Hall $ Chandler 6978; 

 Bishop, Hall $ Chandler 7276. 



Eefs. CHORIZANTHE THURBERI Wats. Proc. Am. Aead. 12: 269 (1877). Var. cryptantha 

 Curran, Bull. Cal. Acad. 1: 275 (1885), type loc. Lancaster. Centrostegia thurberi Gray; 

 Benth. in DC. Prodr. 14: 27 (1856), type loc. San Felipe, Thurber; Torr. Pac. E. Eep. 7 3 : 

 20, pi. 8 (1856). 



10. OXYTHECA Nutt. 



Slender annuals with the internodes more or less covered with stipitate glands 

 and a repeatedly dichotomous inflorescence. Leaves in a rosette at base. 

 Bracts more or less connate, often in 3s. Involucres 2 to several-flowered, more 

 or less pedicellate, mostly turbinate, 4 or 5-cleft, each lobe bearing a bristle or 

 awn. Flowers mostly exserted. Calyx glandular or pubescent on the outside. 

 Stamens 9. Achene commonly lenticular. About 8 Pacific Coast species in 

 North America and 1 in Chile. (Greek oxus, sharp, and theke, case, in allu- 

 sion to the spiny involucre.) 

 Involucres lobed. 



Involucres 5-lobed; bracts united only at base. 



Involucres deeply parted into linear to obovate lobes. 



Plants prostrate; involucres sessile 1. 0. luteola. 



Plants erect; involucres pedicelled. 



Calyx-lobes entire 2. 0. caryophylloides. 



Calyx-lobes cleft 3. 0. trilobata. 



Involucre a shallowly-lobed concave disk; calyx-lobes fimbriate 4. 0. emarginata. 



Involucres acutely 4-lobed; plants erect. 



Bracts completely united into a round concave perfoliate disk; involucres sessile or 



nearly so 5. 0. perfoliata. 



Bracts united only at base; involucres mostly pedicelled. 



Leaves revolute 6. 0. dendroidea. 



Leaves plane 7. 0. watsonii. 



Involucral tube short, not lobed, its margin with 14 to 21 bristles 8. 0. parishii. 



1. 0. luteola Parry. Stems prostrate, several from the base, branching, 2 

 to 5 inches long; herbage usually yellowish; leaves basal and in pairs at the 

 lower nodes, rounded, 1 to 2 lines long, the petioles mostly longer ; bracts linear, 

 acerose, in 2s or 3s; involucres in the forks and along the branchlets, parted 

 almost to the base into 5 unequal divisions, the divisions linear, acerose or 



