12 



ASCLEPIADACEAE. 



[Vol. III. 



20. Asclepias perennis Walt. Thin- 

 leaved Milkweed. (Fig. 2919.) 



Asclepias perennis Walt. Fl. Car. 107. 1788. 



Puberulent above, glabrous below; stem slen- 

 der, simple or branched, erect, sometimes 

 slightly woody at the base, i°-3° high. Leaves 

 thin, opposite, lanceolate, oblong or ovate- 

 lanceolate, slender-petioled, acuminate or acute 

 at both ends, 2'-6' long, )i'-\' wide, glabrous 

 or very nearly so; umbels solitarj', or several 

 and corymbose; peduncles \'-i' long; pedicels 

 very slender, Yz'-i' long; flowers very small, 

 white; corolla-segments oblong, i"-2" long; 

 column about ,'i" high; hoods oval, erect, en- 

 tire, about as long as the anthers, shorter than 

 the subulate-filiform incurved horn; follicles 

 glabrous, erect on the erect fruiting pedicels; 

 seeds $"-(>" long, 3>^"-4^" wide, very thin, 

 destitute of coma. 



On river-shores and in wet places, North Carolina 

 to southern Illinois and Missouri, south to Florida 

 and Te.xas. MaT-.\ug. 



21. Asclepias verticillata L. Whorled 

 ^lilkweed. (,Fig. 2920.) 



Asclepias verticillata L. Sp. PI. 217, 1753. 



Roots fascicled ; stem slender, simple or branched, 

 pubescent in lines at least above, very leafy, i°- 

 2K° bigh. Leaves narrowly linear, sessile, verti- 

 cillate in 3's-7's or some of them alternate, gla- 

 brous or very nearly so, their margins narrowly 

 revolute; umbels usually numerous, many- flow- 

 ered; peduncles slender, ]z'-T.Vz' long; pedicels 

 almost filiform, shorter than the peduncles; cor- 

 olla greenish white, its segments oblong, i|^"-2" 

 long; column about H" high; hoods white, ob- 

 long, entire, about equalling the anthers, much 

 shorter than the subulate incurved horn; follicles 

 erect on the erect fruiting pedicels, narrowly 

 spindle-shaped, glabrous, 2'-3' long. 



In dry fields and on hills, Maine and southern On- 

 tario to the Northwest Territor5', south to Florida, 

 Mexico and New Mexico. July-Sept. 



1^1 



22. Asclepias pumila fA. Gray) Vail. 



Low Milkweed. (Fig. 2921.) 



Asclepias verticillata var. pumila A. Gray, Proc. 



Am. Acad. 12: 71. 1S76. 



Stems 4'-io' high, tufted from a woody 

 root. Leaves very numerous, crowded, some- 

 times obscurely whorled, filiform-linear, i'-2' 

 long, smooth or minutely roughened, the mar- 

 gins revolute; umbels 2-several, short-pedun- 

 cled, few-flowered; pedicels filiform, puberu- 

 lent, 3"-4" long; corolla greenish white, its 

 segments oblong, i '2 "-2" long; column short; 

 hoods white, erect, oblong, entire, equalling 

 the anthers, shorter than the slender incurred 

 horn; follicles erect on erect fruiting pedicels, 

 narrowly spindle-shaped, l'2'-2' long, finely 

 puberulent. 



Dry plains. South Dakota to Arkansas, Colo- 

 rado and New Mexico. 



