554 FLORA. 



Leaflets 7-21, oblong, elliptic or ovate ; flowers white. 



Pod stalked ; flowers slender-pedicelled. I. P. Americana. 



Pod sessile ; flowers short-pedicelled. 2. P. neglect j. 



Leaflet only 1, or sometimes 3-5, very narrowly linear; flowers pink. 3. P. longifolia. 



1. Phaca Americana (I look.) Rydberg. Arctic Milk Vetch. (I. F. f. 

 2148.) Erect, nearly simple, glabrous, 3-6 dm. high. Stipules foliaceous, ovate- 

 oblong, 4-12 mm. long; leaflets 7-17, 2-4 cm. long ; peduncles generally exceeding 

 the leaves; flowers 16-19 mm - long, in loose racemes; pedicels filiform, 13 mm. 

 long in fruit; pod stipitate, 21-25 mm - l° n g> acute at each end, oblong, dehiscent 

 at maturity, glabrous, shining. In wet rocky places, Quebec and arctic Am. to 

 Br. Col. and Alaska, south in the Rocky Mts. to Colo. June-July. 



2. Phaca neglecta T. & G. Cooper's Milk Vetch. (I. F. f. 2149.) Gla- 

 brous or nearly so, 3-6 dm. high. Stipules ovate, acute, 2-4 mm. long; leaflets 

 9-21, thin, oblong or elliptic, often minutely pubescent beneath, 16-25 mm - l° n g> 

 obtuse or emarginate, narrowed at the base; flowers 11-15 mm. long, in loose 

 spikes; calyx pubescent with blackish hairs, its teeth subulate ; pod sessile, the 

 ventral suture somewhat intruded, ovoid, acute, glabrous, slightly furrowed along 

 both sutures, 13-20 mm. long. On banks and shores, Quebec to Minn, and Iowa. 

 June-July. 



3. Phaca longifolia (Pursh) Nutt. Long-leaved Milk Vetch. (I. F. f. 

 2150.) Erect, slender, finely canescent, 1.5-4.5 dm. high. Stipules subulate, rigid, 

 those of the lower part of the stem connate; leaflet usually 1, nearly terete, 2.5-10 

 cm. long, sometimes 3 or 5; flowers few, 6-1 1 mm. ldng, in short loose racemes; 

 peduncles shorter than the leaves ; pod short-stalked, spotted, glabrous, ovoid, 

 short-pointed, not furrowed, about 2.5 cm. long. In sandy soil, Neb. to Kans. and 

 N. Mex. Leaves persistent. May-June. 



25. HOMALOBUS Nutt. 



Perennial herbs, with pinnate simple or pinnately 3-5-foliolate leaves, and race- 

 mose mostly small flowers, the peduncles short or elongated. Keel of the corolla 

 obtuse; pod flat, glabrous or pubescent, completely 1 celled, few-several-seeded, 

 the sutures both prominent externally. [Greek, regular-lobes.] Besides the fol- 

 lowing species, some 30 others occur in western N. Am. 



Plants leafy-stemmed. 



Leaves pinnate ; leaflets 0-23, thin. 



Finely pubescent, blackening in drying ; pod straight. 1. //. tenellus. 



Canescent, not blackening ; pod slightly curved. 2. H. aborigi?ium. 



Leaves pinnate ; leaflets 3-7, rigid, very narrow, spiny. 3. H. montanus. 



Plant scapose ; leaves simple or pinnately 3-5-foliolate, the leaflets very narrow. 



4. //. caespitesus, 



1. Homalobus tenellus (Pursh) Britton. Loose-flowered Milk Vetch. 

 (I. F. f. 2151.) Finely pubescent or glabrate, 2.5-4.5 dm. high. Stipules broadly 

 ovate, 3-6 mm. long, the upper ones connate; leaflets oblong, linear-oblong or ob- 

 lanceolate, obtuse, narrowed at the base, 13-21 mm. long; flowers yellowish-white, 

 6-9 mm. long, in loose spike-like racemes; pod stalked, straight, oblong, acute at 

 each end, papery, glabrous, 13-17 mm. long. Dry soil, S. Dak., Neb. and Colo, 

 to Cal., the N. W. Terr, and Br. Col. May-Aug. 



2. Homalobus aboriginum (Richards.) Rydberg. Indian Milk Vetch. (I. F. 

 f. 2145.) Finely canescent, 2-5 dm. high. Stipules ovate, acute, 4-6 mm. long; 

 leaflets 9-13, linear or oblong, 12-21 mm. long; flowers 9-11 mm. long, in rather 

 loose racemes; peduncles longer than the leaves; pod compressed, oval in section, 

 half-elliptic, long-stipitate, acute at each end; calyx blackish-pubescent, its teeth 

 subulate. S. Dak. to Manitoba, the N. W. Terr, and Colo. {Astragalus aborigi- 

 num Richards.] May-June. 



3. Homalobus montanus (Nutt.) Britton. Prickly Milk Vetch. (I. F. f. 

 2152.) Densely tufted, intricately branched, 5-25 cm. high, finely canescent. 

 Stipules linear-lanceolate, spiny-tipped, 4-1 1 mm. long; leaflets linear, -widely 

 spreading, 6-13 mm. long; flowers 1-4 together in the axils, nearly sessile, 

 yellowish white or bluish-tinged, 4 6 mm. long; pod sessile or short-stalked, 

 1-3-seeded, ovoid-oblong, acute, coriaceous, dehiscent, pubescent, 6-9 mm. long. 

 In dry, rocky places, Neb. to N. Mex., N<v. :U k1 the X. YY. Terr. June-Sept. 



