462 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



33. Dalea grayi (Vail) L. O. Williams, Mo. Bot. Gard. Ann. 23: 450. 



1936. 



Parosela grayi Vail, Torrey Bot. Club Bui. 24: 14. 1897. 

 Thornbera grayi Rydb., North Amer. Fl. 24: 119. 1920. 



Graham, Gila, Cochise, Santa Cruz, and Pima Counties, 3,500 to 

 5,500 feet, hills and mountains, May to September. New Mexico, 

 Arizona, Sonora, and Durango. 



34. Dalea albiflora A. Gray, PL Wright. 2: 38. 1853. 



Parosela albiflora Vail, N. Y. Acad. Sci. Trans. 14: 34. 1894. 

 Thornbera albiflora Rvdb., N. Y. Bot. Gard. Jour. 20: 66 



1919. 

 Thornbera villosa Rydb., North Amer. Fl. 24: 118. 1920. 

 Thornbera albiflora subsp. villosa Wiggins, Dudley Herbarium 



Stanford Univ. Contrib. 3: 54. 1940. 



Hualpai Mountain (Mohave County) to Cochise, Santa Cruz, and 

 Pima Counties, 3,500 to 7,500 feet, April to October. New Mexico, 

 Arizona, Sonora, and Chihuahua. 



Dalea ordiae A. Gray is distinguished by smaller, narrower, and 

 usually more numerous leaflets, and more slender stems, but the 

 characters are not strongly correlated and the species appears to 

 intergrade completely with D. albiflora. Thornbera villosa is a robust 

 form with very villous stems. A peculiar form of D. albiflora col- 

 lected on East Fork of White River (Harrison 4835) and in the Sierra 

 Ancha (Harrison and Kearney 8311) probably represents a distinct 

 variety. In this form the caudex is wanting, the small slender stems 

 arising at intervals from rootstocks. 



28. PETALOSTEMUM. Peairieclover 



Plants herbaceous, annual or perennial, often deep-rooted; herbage 

 gland-dotted; leaves odd-pinnate, the leaflets several or numerous; 

 flowers in dense spikes, only slightly irregular; petals white, lilac, or 

 rose pink, the claws of the wings and keel adnate to the stamen tube; 

 stamens 5; pods small, included in the calyx, containing 1 or 2 seeds. 



The plants are attractive but of small economic importance. The 

 name of the genus is often spelled Petalostemon. 



Key to the species 



1. Calyx tube glabrous or sparsely puberulent, the lobes ciliolate, about one-third 

 as long as the very prominently 10-ribbed tube; plant perennial; stems and 

 leaves glabrous; leaflets 3 to 9, commonly 5, linear-oblanceolate; petals 

 white; blade of the banner cordate or reniform, wider than long. 



1. P. CANDIDUM. 



1 . Calyx tube pilose or villous (2) . 



2. Plant annual; stems slender, glabrous; leaflets 3 to 5, linear, very acute, 1 tp 



3 cm. long, glabrous; spikes long-peduncled, slender, about 6 mm. in 



diameter in fruit; bracts conspicuous, dark colored, elliptic, ovate, or 



rhombic, subulate-tipped; corolla lilac, about 4 mm. long; blade of the 



banner shorter than the claw 2. P. exile. 



2. Plants perennial (3) . 



3. Corolla white; blade of the banner equaling or longer than the claw, 

 quadrilateral ; leaflets 3 to 7 ; stems glabrous or sparsely pilose, rather 

 conspicuously glandular-punctate; peduncles 10 to 20 cm. long; spikes 

 10 to 12 mm. in diameter 3. P. flavescens. 



