FLOWERING PLANTS AND FERNS OF ARIZONA 237 



single, folded, 2-lobed, dentate bract, this in fruit enlarged, scarious, 

 reticulate-veined, bigibbous on the back. 



1. Pterostegia drymarioides Fisch. and Meyer, Index Sem. Hort. 

 Petrop. 2: 23. 1835. 

 Pinal, Maricopa, Pima, and Yuma Counties, 3,000 feet or lower, 

 February to April. Oregon to Utah, Arizona, and Baja California. 



2. CHORIZANTHE s* 



Plants annual, herbaceous, dichotomously branched; foliage leaves 

 in a basal rosette, soon disappearing, the stem leaves mostly bractlike, 

 opposite or in 3's; flowers (usually solitary) in a tubular or funnelform 

 involucre ; stamens commonly 9. 



Plants of the more desertic parts of the State. 



Key to the species 



1. Bracts divergently 3-lobed; involucre small, with 3 rather broad divaricate 

 spurs at base; plant often reddish; stems glandular-puberulent, especially 

 toward the base, slender, diffusely branched, not becoming rigid; foliage 

 leaves all basal, oblanceolate or spatulate; teeth of the bracts and involucre 



straight 1. C. thurberi. 



1. Bracts entire; involucre not spurred (2). 



2. Involucres 6-toothed, the tube 6-ribbed, the teeth strongly hooked at apex; 

 stems very brittle, soon disarticulating; foliage leaves all basal, narrowly 

 oblanceolate, strigose or villous, the stem leaves reduced to subulate 



bracts 2. C. brevicornu. 



2. Involucres with fewer than 6 teeth, the tube either 3-ribbed (angled) or not 

 ribbed; stems not very brittle; stem leaves, at least the lower ones, very 

 like the basal leaves, the blades woolly beneath (3) . 

 3. Tube of the involucre 3-angled, much shorter than the teeth, with promi- 

 nent transverse ridges; leaf blades mostly broadly elliptic or suborbic- 

 ular, shorter than the petioles; teeth of the involucre very unequal, 

 leaflike, the spiny tips (and those of the bracts) straight. 



3. C. RIGIDA. 



3. Tube of the involucre not angled, cylindric, nearly equaling to longer than 

 the teeth, cross-corrugate, the teeth hooked (4). 

 4. Involucral teeth 5, unequal, one much larger than the others and often 

 leaflike; blades of the basal leaves oblanceolate; tube of the in- 

 volucre at maturity 4 to 6 mm. long, much longer than the teeth. 



4. C. WATSONI. 



4. Involucral teeth 3, equal or nearly so; blades of the basal leaves ovate or 



suborbicular; tube of the involucre 2 to 3 mm. long, about as long 



as the teeth 5. C. corrugata. 



1. Chorizanthe thurberi (A. Gray) S. Wats., Amer. Acad. Arts and 



Sci. Proc. 12: 269. 1877. 



Centrostegia thurberi A. Gray ex Benth. in DC, Prodr. 14: 27. 

 1856. 



Mohave, Yavapai, Graham, Gila, and Maricopa Counties, 4,000 feet 

 or lower, in sandy soil, March to May. Arizona, Nevada, and 

 California. 



2. Chorizanthe brevicornu Torr., U. S. and Mex. Bound. Bot. 177. 



1859. 

 Mohave, Graham, Maricopa, Pinal, Pima, and Yuma Counties, 

 2,700 feet or lower, March to May. Arizona, Nevada, and California. 



** Reference: Goodman, G. J. a revision of the north American species of chorizanthe. Mo, 

 Bot. Gard. Ann. 21: 1-102. 1934. 



