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

 23. PSORALEA. Scurf-pea 



Plants perennial, herbaceous ; flowering stems from a thick tuberlike 

 taproot or from branched rootstocks, scapose or leafy; herbage 

 glandular-punctate; leaves digitately 3- to 5-foliolate; inflorescences 

 axillary or appearing terminal in the scapose species; calyx regular or 

 irregular; pods small, ovoid, indehiscent, 1 -seeded. 



The tuberous-rooted species, known as breadroot, were used for 

 food by the Indians and early white settlers. P. lanceolata is an 

 admirable soil, binder in sandy areas in northern Arizona but is 

 sometimes a troublesome weed in fields, as it propagates by creeping 

 rootstocks. Its presence is often an indication of overgrazing. P. 

 tenuiflora has been reported to poison horses and cattle. 



Key to the species 



1. Flowering stems from a very thick, tuberous, rounded or fusiform taproot; 



plants conspicuously pubescent, often subacaulescent, the main stem not 



more than 10 cm. long; leaves prevailingly 5-foliolate; leaflets broadly 



obovate to nearly orbicular; inflorescence conspicuously bracteate, very 



dense; pods regularly or irregularly circumscissile near the middle, the 



beak equaling or longer than the body of the pod: Section Pediomelum (2). 



2. Lowest calyx lobe much more than twice as wide as the others, resembling 



the bracts; seeds transversely wrinkled; petioles appressed-pubescent: 



leaflets cuneate-obovate or rhombic; inflorescence 2 to 4 cm. long; 



corolla not more than 10 mm. long 1. P. castorea. 



2. Lowest calyx lobe about twice as wide as the others; seeds smooth (3). 

 3. Hairs of the petiole and peduncle all appressed or ascending; corolla about 

 20 mm. long; leaflets cuneate-obovate; inflorescence about 2 cm. long. 



2. P. MEGALANTHA. 



3. Hairs of the petiole and peduncle (the longer ones) spreading or retrorse; 

 corolla 10 to 17 mm. long; inflorescence 2 to 7 cm. long. 



3. P. MEPHITICA. 



1. Flowering stems from branched rootstocks, the roots not tuberous-thickened; 

 plants not conspicuously pubescent, strongly caulescent, the main stem 

 seldom less than 20 cm. long; leaves mostly 3-foliolate; leaflets narrowly 

 obovate, oblanceolate, or linear; inflorescence inconspicuously bracteate, 

 loose or moderately dense; pods indehiscent, the beak much shorter than 

 the body of the pod, the surface glandular- warty : Section Psoralidium (4). 

 4. Corolla whitish, the tip of the keel often purple; pods subglobose, rounded 

 and abruptly beaked at apex; leaves all trifoliolate; leaflets oblanceolate 



to nearly filiform 4. P. lanceolata. 



4. Corolla violet; pods ovoid, somewhat tapering into the beak; lower leaves 

 often 4- or 5-foliolate (5) . 

 5. Leaves (except those near the base of the flowering stems), reduced to 

 small, subulate scales; flowers few, distant, subsessile; pods white- 

 sericeous 5. P. JUNCEA. 



5. Leaves well developed, mostly 3-foliolate; flowers numerous, usually 

 distinctly pedicelled, the pedicels 1 to 4 mm. long; pods glabrous. 



6. P. TENUIFLORA. 



1. Psoralea castorea S. Wats., Amer. Acad. Arts and Sci. Proc. 14: 

 291. 1879. 



Pediomelum castor eum Rydb., North Amer. Fl. 24: 22. 1919. 



Northern Mohave County, at Beaver Dam and Pagumpa Springs, 

 2,000 to 4,000 feet, sandy soil, April and May, type from between 

 Beaver Dam, Ariz., and St. Thomas, Nev. {Palmer). Southern Utah 

 and northwestern Arizona to southeastern California. 



