744 FLORA. 



the recurved fruiting pedicels, 7-10 cm. long. In moist soil, Minn, to Br. Col. 

 Kans., Utah and Cal. May-July. 



17. Asclepias arenaria Torr. SAND MILKWEED. (I. F. f. 2916.) Densely 

 tomentose-canescent all over ; stems simple, ascending or erect, stout, 3-6 dm. 

 high. Leaves obovate or oval, thick, obtuse or retuse and cuspidate at the apex, 

 truncate, subcordate, obtuse, or rarely some of them narrowed at the base, 510 

 cm. long, the angle of the primary nervation broad; umbels densely many-flowered, 

 short-peduncled or sessile; corolla greenish white, its segments oval oblong; hoods 

 oblong, truncate at each end, oblique at the apex, longer than the anthers, with a 

 broad tooth on each side within; horn semi-lunate with an abruptly incurved sub- 

 ulate apex; follicles puberulent, 5-10 cm. long, erect on the decurved fruiting pedi- 

 cels. On sand-bars and hills, Neb. and Colo, to Mex. and N. Mex. June-Sept. 



18. Asclepias ovalifdlia Dec. OVAL-LEAVED MILKWORT. (I. F. f. 2917.) 

 Finely tomentose all over; stem simple, usually slender, erect, 3-6 dm. high. 

 Leaves oval, ovate, oblong 'or ovate-lanceolate, 5-8 cm. long, short-petioled, the 

 upper surfaces becoming glabrate; umbels solitary or few, many-flowered; pedun- 

 cles short; corolla greenish-white or purplish, its segments ovate-oblong, obtuse; 

 hoods oval-oblong, nearly twice as long as the anthers, bearing a large acute tooth 

 on each of the inner margins; horn subulate, incurved over the stigma; follicles 

 ascending on the reflexed fruiting pedicels, pubescent. In woods and on prairies, 

 111. to S. Dak., Manitoba and the N. W. Terr. June-July. 



19. Asclepias brachystephana Engelm. SHORT CROWNED MILKWEED. 

 (I. F. f. 2918.) Puberulent when young, soon glabrate; stems clustered, often 

 branched, spreading or ascending, 15-25 cm. long. Leaves lanceolate or linear- 

 lanceolate, long-acuminate, 5-8 cm. long, or the lowest shorter; umbels several, 

 terminal and axillary, few-flowered; peduncles short; pedicels equalling or longer 

 than the peduncles; corolla greenish purple, its segments about 4 mm. long; hoods 

 ovate, obtuse, shorter than the anthers, the short erect-incurved horn slightly ex- 

 serted; follicles erect on the spreading or decurved fruiting pedicels, downy or 

 hoary, acuminate. 5-9 cm. long. In dry soil, Kans. (according to B. B. Smyth), 

 Wyo. to Tex., Ariz, and Mex. June-Aug. 



20. Asclepias perennis Walt. THIN-LEAVED MILKWEED. (I. F. f. 2919.) 

 Puberulent above, glabrous below ; stem slender, erect, sometimes slightly woody 

 at the base, 3-9 dm. high. Leaves lanceolate, oblong or ovate-lanceolate, acumin- 

 ate or acute at both ends, 5-15 cm. long, glabrous or nearly so ; umbels solitary, 

 or several and corymbose; peduncles 2.55 cm< ^ on 5 pedicels slender; flowers very 

 small, white ; corolla-segments oblong, 2-4 mm. long ; hoods oval, erect, entire, 

 about as long as the anthers, shorter than the subulate-filiform incurved horn ; 

 follicles glabrous, erect on the erect fruiting pedicels; seeds 11-13 mm. long, very 

 thin, destitute of coma. On river-shores and in wet places, N. Car. to 111., Mo., 

 Fla. and Tex. May-Aug. 



21. Asclepias verticillata L. WHORLED MILKWEED. (I. F. f. 2920.) 

 Roots fascicled; stem slender, pubescent in lines at least above, very leafy, 3-8 dm. 

 high. Leaves narrowly linear, sessile, verticillate in 3's~7's or some of them 

 alternate, glabrous or nearly so, their margins narrowly revolute ; umbels usually 

 numerous, small; peduncles slender ; pedicels filiform; corolla greenish white, its 

 segments oblong, 3-4 mm. long; hoods white, oblong, entire, about equalling the 

 anthers, much shorter than the subulate incurved horn ; follicles erect on the 

 erect fruiting pedicels, narrowly spindle-shaped, glabrous, 5-7 cm. long. Dry fields 

 and hills, Me. and Ont. to th'e N. W. Terr., Fla., Mex. and N. Mex. July-Sept. 



22. Asclepias galioides H. B. K. BEDSTRAW MILKWEED. (I. F. f. 292oa.) 

 Glabrous, except the minutely pubescent stems and pedicels. Stems erect, 3-5 dm. 

 high from a horizontal rootstock ; leaves erect or spreading, in whorls of 2-6, 

 narrowly linear, 5-8 cm. long, the margins revolute; peduncles longer than the 

 pedicels and shorter than the leaves; umbels 19-26 mm. in diameter; flowers 

 greenish-white; corolla-segments 4 mm. long; hoods as high as the anthers, broadly 

 rounded at the summit, dorsally hastate-sagittate, the ventral margins slightly in- 

 volute, entire; horn arising from the base of the hood, long-exserted over the 

 anthers; anther- wings minutely notched at the base; follicles erect on erect fruiting 

 pedicels, attenuated, 5-7 cm. long, glabrous or nearly so. Kans. to Colo., Ariz, 

 and Mex. May -July. 



