PEA FAMILY 507 



6-10 mm. long, ovoid. A. ytiicrolobus A. Grviy. Plains and hills : S.D. — Kans. — 

 Colo. — Mont. Plain — Submont. Je-Jl. 



32. PTEROPHACOS Rydb. 



Perennial glabrous or strigose herbs. Leaves alternate, odd-pinnate, with 

 nearly free and distinct stipules; leaflets linear or linear-filiform, scarcely broader 

 than the rachis. Flowers perfect, in short racemes. Calyx-tube oblong-cam- 

 panulate, with short subulate-setaceous teeth. Corolla white; banner narrow. 

 Stamens 10; filaments diadelphous; anthers alike. Legume woody, one-celled, 

 2-valved, the valves winged on the back, the sutures acute or even winged. 

 Seeds many. 



1. P. tetrapterus (A. Gray) Rydb. Stem about 3 dm. high, glabrous, 

 striate; leaflets 15-21, narrowly linear, 12-20 mm. long, 1-2 mm. wide; raceme 

 short, 5-9-flowered; calyx-teeth setaceous-subulate, about half as long as the 

 tube; corolla white, about 15 mm. long; pod 3-4 cm. long, arcuate, glabrous, 

 4-winged, 8 mm. wide. ^4. tetrapterus A. Gray. Dry ground: s Utah. Son. 



33. ATELOPHRAGMA Rydb. 



Caulescent leafy slender perennial herbs, with rootstocks. Stipules nearly 

 free both from each other and from the petioles. Leaves pinnate, usually with 

 numerous leaflets. Inflorescence a spike-like raceme. Calyx short, campanu- 

 late; lobes slender, subulate. Corolla white or purplish. Pod membranous or 

 papery, more or less compressed laterally, in the typical species decidedly flat- 

 tened and stipitate; dorsal suture intruding in the pod and forming a partial 

 partition. 



Pod stipitate, flat. 



Partial partition broad, making the pod almost 2-celled. 1. A. Arthuri. 



Partial partition narrow, less than one-tliird the ^vidth of the pod. 

 Pod long-stipitate, glabrous at least in age. 



Plant loosely short-villous. 2. A. aboriginum. 



Plants appressed-silky or glabrous. 



Leaflets oblong. .3. A. Forwoodii. 



Leaflets linear. 



Plant graj-ish silky. 4. A. linear e. 



Plant glabrous or with a few scattered hairs. 5. .4. glabriusculum. 



Pod short-stipitate, hairy. 



Upper leaves not reduced; pod black-hairy. 6. A. Macounii. 



Upper leaves reduced, often unifoliolate; pod not black-hairy. 



7. A. ibapense. 

 Pod sessile, more turgid. 



Racemes many-flowered ; leaflets oblong ; partition of the pod narrow. 



Racemes elongate; pod short-obovoid. 8. A. elegans. 



Racemes shorty pod oblong. 9. A. Shearii. 



Racemes few-flowered; leaflets linear; partition of the pod broad. 



10. A. Brandegei. 



1. A. Arthur! (M. E. Jones) Rydb. Stems 3^ dm. high, finely strigose; 

 leaflets 21-35, oblong-elliptic, obtuse or retuse, 5-10 mm. long, glabrous above, 

 minutely strigose beneath; racemes about 1 dm. long; calyx black-hairy; tube 

 5 mm. long; teeth 3 mm. long; corolla 10-12 mm. long, white; pod strigose; stipe 

 8-10 mm. long; body linear, 3-3.5 cm. long, tapering at both ends. Astragalus 

 Arthuri M. E. Jones. Basalt hillsides: Ida. Son. — Submont. Je. 



2. A. aboriginum (Richards.) Rydb. Stems 2-4 dm. high, short-villous; 

 leaflets 9-15, linear-oblong to elliptic or lanceolate, 1-2 cm. long; raceme short; 

 calyx more or less black-hairy; tube 3-4 mm. long; teeth 2-3 mm. long; corolla 

 ochroleucous, 9-11 mm. long; pod glabrous; stipe 5-8 mm. long; body oblance- 

 olate, acute at both ends, 1.5-2 cm. long; lower suture almost straight. 

 Astragalus aboriginorum Richards. Mountains: Sask. — Colo. — Nev. — Yukon. 

 Submont. — Mont. My-Je. 



3. A. Forwoodii (S. Wats.) Rydb. Stems ascending, minutely strigose, 

 1-3 dm. high; leaflets 9-17, oblong or oblanceolate, strigose on both sides or gla- 

 brous above, 1-1.5 cm. long; raceme short; calyx more or less black-hairy; tube 

 3 mm. long; teeth 2 mm. long; legume glabrous, flat; stipe 3-5 mm. long; body 

 2-2.5 cm. long, lunate-oblanceolate; lower suture usually somewhat concavely 



