486 FABACEAE 



united at the base. Corolla yellow or straw-colored; banner obovate, emar- 

 ginate, recurved; wings oblong, obtuse; keel incurved, very obtuse, shorter than 

 the wings. Stamens 10, diadelphic. Style filiform, barbate at the apex; stigma 

 terminal, barbate. Legume linear; flat, short-stipitate, few-seeded. Seeds 

 oval, compressed. 



Leaflets linear-elliptic or lanceolate, acute and mucronate, 2-6 mm. long, or wanting; 



corolla 12-15 mm. long. 1. P. scoparia. 



Leaflets broadly elliptic, oval, or obovate, rounded and mucronate at the apex, 8-15 



mm. long. 2. P. Thompsonae. 



1. P. scoparia A. Gray. Stem woody at the base, 5-10 dm. high, with 

 ascending branches; stipular spines slender, 3-5 mm. long; leaflets 9-15, linear- 

 elliptic or lanceolate, acute at both ends, 2-6 mm. long, sparingly strigose; some 

 of the leaves reduced to merely the slender rachis; racemes 2-3 dm. long, lax; 

 calyx about 1 cm. long; teeth half as long as the tube; legume about 5 cm. long 

 or more, about 6 mm. wide. Valleys: w Tex. sw Colo. N.M. Chihuahua. 

 Son. Je-Jl. 



2. P. Thompsonae S. Wats. Herbaceous, with rather simple stem, sparingly 

 strigose when young, 3-4 dm. high; leaflets 13-21, oval or obovate or broadly 

 elliptic, rounded at both ends, 8-15 mm. long, grayish strigose on both sides, 

 mucronate; raceme dense; pedicels and calyx glandular, as well as strigose; 

 calyx 10-15 mm. long, the lanceolate or subulate teeth equalling the tube; corolla 

 15-20 mm. long; legume about 5 cm. long and 4 mm. wide. Dry rocky cliffs: 

 Utah. Son. My-Jl. 



18. PHACA L. RATTLE- WEED, RATTLE-POD. 



Perennial or annual herbs, caulescent or rarely almost stemless. Leaves 

 alternate; stipules nearly free from the petioles, often partially united with each 

 other; leaflets many or few, entire, or in one species often none. Flowers perfect, 

 racemose, or in one species subsessile in the axils of the leaves. Calyx campanu- 

 late. Corolla ochroleucous or purple; banner rather broad; wings longer than 

 the keel; the latter beakless. Stamens 10, diadelphous; anthers alike. Pod 

 membranous, inflated, sessile or stipitate, 1-celled, with neither suture intruded, 

 without even a partial partition. Seeds numerous. 



Upper suture of the pod not acute; pod circular or oval in cross-section. 

 Pod stipitate. 



Pod long-stipitate, not mottled; stipe longer than the calyx. 



Pod pendent; flowers ochroleucous. 1. P. americana. 



Pod on an ascending stipe; flowers purplish. 2. P. ampularia. 



Pod short-stipitate; stipe scarcely exceeding the calyx. 

 Pod not mottled, erect or ascending. 

 Pod ashy-strigose, with minute hairs. 



Pods sulcate above; leaflets broad. 3. P. Wetherillii. 



Pod not sulcate; leaflets narrow. 4. P. allochroa. 



Pod glabrous. 



Flowers purplish; racemes long-peduncled ; pods about 2 cm. long. 



5. P. Eastwoodiae. 

 Flowers white; racemes short-peduncled ; pods 3-4 cm. long. 



6. P. lutosa. 

 Pod mottled, spreading or reflexed. 



Leaflets linear or none; plant grayish pubescent. 



Terminal leaflet none, represented by the much produced rachis ; lateral 



leaflets often also lacking. 7. P. longifolia. 



Leaflets present; rachis not produced. 



Stem canescent, 1-2 dm. high; calyx-teeth subulate. 



8. P. picta. 

 Stem glabrous or nearly so, 3-5 dm. high; calyx-teeth triangular. 



9. P. Cusickii. 

 Leaflets elliptic to broadly oval or obcordate. 



Plant glabrous. 10. P. artipes. 



Plant canescent. 11. P. Hookeriana. 



Pod sessile. 



Pod more than 12 mm. long. 



Plant densely cespitose, almost stemless; pod 3.5-5 cm. long. 



12. P. megacarpa. 

 Plant distinctly caulescent and leafy; pod 3 cm. long or less. 



Whole plant glabrous. 13. P. Wardii. 



Plant, including the pods, pubescent. 



Calyx-teeth very short, scarcely one-third as long as the tube. 



14. P. subcinerea. 



