30S NORTH AMERICAN FLORA [Volume 24 



39. PTEROPHACOS Rydb. Fl. Rocky Mts. 507, 1063. 1917. 



Perennial, glabrous or strigose herbs, with a woody cespitose caudex. Leaves odd-pinnate, 

 with linear-filiform leaflets, scarcely broader than the rachis; stipules nearly free and distinct. 

 Flowers perfect, borne in short racemes. Calyx-tube oblong-campanulate; teeth short, 

 subulate. Corolla white or purplish. Banner narrow, oblanceolate, only slightly arched. 

 Wings shorter, narrow, the blade narrowly oblong-oblanceolate or linear-oblong, with a re- 

 flexed basal auricle, about equaling the slender claw. Keel-petals still shorter, the blade lunate, 

 with a rather prominent, reflexed auricle. Stamens diadelphous (9 and 1), the sheath nearly 

 straight to near the truncate apex, the free portion of the filaments arched upwards. Ovary 

 sessile, the style glabrous, slightly arched throughout; stigma minute. Pod woody, one-celled, 

 sessile, cross-reticulate, 2-valved, the valves winged on the back, the sutures prominent or even 

 winged. Seeds many, very obliquely lunate. 



Type species, Astragalus tetrapterus A. Gray. 



Pod flat and oval, ovate, or lanceolate in outline; sutures not winged. 1. P. pterocarpus. 

 Pod 4-angled, oblong, falcate; sutures wing-margined. 



Plant, including the pod, glabrous or nearly so; leaflets obtuse, linear-filiform. 2. P. tetrapterus. 



Plant caneseent; pod strigose; leaflets lanceolate, acute. 3. P. cinerascens. 



1. Pterophacos pterocarpus (S. Wats.) Rydberg. 



Astragalus pterocarpus S. Wats. Bot. King's Expl. 71. 1871. 

 Tragacantha pterocarpa Kuntze, Rev. Gen. 947. 1891. 



A perennial, forming clumps; stems several, decumbent at the base, branched, 3-5 dm. 

 high, striate, sparingly strigose; leaves ascending, strigose, 5-10 cm. long, the rachis margined; 

 stipules deltoid, 4-5 mm. long; leaflets 5-9, linear-filiform, similar to the rachis and indistinctly 

 jointed to it, 2-5 cm. long, about 1 mm. wide, strigose, caneseent when young; peduncles 8-15 

 cm. long; racemes 3-5 cm. long; bracts lanceolate, 1-2 mm. long; pedicels 2 mm. long; calyx 

 pilose, usually with mixed white and black hairs, the tube 7-8 mm. long, 2.5-3 mm. broad, 

 the teeth subulate, 2 mm. long; corolla purple, 15-17 mm. long; banner obovate, moderately 

 arched; wings 12-13 mm. long, the blade obliquely oblanceolate, falcate, with a large reflexed 

 auricle; keel-petals slightly shorter, the blade oblong, falcate, with a large reflexed auricle; 

 pod obeompressed, oval-ovate or lanceolate in outline, 3.5-4 cm. long, 15-18 mm. thick, and 

 3 mm. wide, the sutures rather prominent but not winged, except at the apex, the pod depressed 

 around the sutures, the cross-section resembling a pair of spectacles. 



Type locality: Junction of Reese River with the Humboldt, Nevada. 



Distribution: Nevada. 



Illustrations: S. Wats. Bot. King's Expl. pi. 12; M. E. Jones, Rev. Astrag. pi. 31, 73. 



2. Pterophacos tetrapterus (A. Gray) Rydb. Fl. Rocky Mts. 507, 

 1063. 1917. 



Astragalus tetrapterus A. Gray, Proc. Am. Acad. 13: 369. 1878. 

 Astragalus tetrapterus capricornus M. E. Jones, Rev. Astrag. 149. 1923. 



A perennial; stems several, decumbent at the base, 1-4 dm. high, glabrous or nearly so, 

 striate, branched; leaves ascending, 5-7 cm. long, the rachis wing-margined; stipules deltoid, 

 3-4 mm. long; leaflets 1 1-17, linear, 1-3 cm. long, 1-2 mm. wide, glabrous or slightly strigose; 

 peduncles 3-6 cm. long; racemes 2-3 dm. long, rather dense; bracts lanceolate, 1-2 mm. long; 

 calyx strigulose with black hairs, the tube 6 mm. long, 2.5-3 mm. broad, the teeth unequal, 

 the lower three subulate, the upper two broader, with a deltoid base, 2 mm. long; corolla white 

 or, according to Jones, purple, 18-20 mm. long; banner narrowly obovate, slightly arched; 

 wing-petals much shorter, the blade linear-oblong; keel-petals still shorter, the blade broadly 

 lunate; pod glabrous, 3-4 cm. long, 7-8 mm. thick and wide, falcate, 4-winged, i.e., both the 

 sutures and the middle of the valves winged. 



Type locality-: Southern Utah. 

 Distribution: Southern Utah and Nevada. 

 Illustration: M. E. Jones, Rev. Astrag. pi. 31. 



