234 asclepiadace.t:. 



Woods. N. Y. to Car, July, Aug. Q\..—Stem 3—4 feet high. Leaves 

 slightly acuminate ,*on pubescent petioles. Umbels 1 4, terminal and on the 

 upper part of the stem, rather densely flowered. Flowers greenish- white, tinged 

 with purple witliin. Variegated Silkxaeed. 



7. A. laurifolia Mich. : stem erect, simple, slightly pubescent ; leaves 

 ovate-lanceolate, very acute, subcordate or often rounded at base, subsessile, 

 somewhat distant, smooth, scabrous-serrate on the margin ; umbels mostly 

 terminal ; leafets of the crown acute, with the horns scarcely as long. 

 A. acuminata Pursk. A. periploccsfolia Nutt. 



Low grounds. N. J. to Car. July, Aug. %. — Root tuberous. Stem 18 inches 

 to 2 feet high. Leaves subsessile or on very short petioles. Umbels 1 — 3, near 

 the summit. Flowers yellowish-green and purple. Laurus-leaved Silkweed. 



8. A. quadrifolia Jacq. : stem simple, slender, smooth ; leaves lance-ovate, 

 acuminate, petiolate, smooth, 4 larger ones in a whorl near the middle of 

 the stem ; umbels 2, terminal, erect, loose ; pedicels capillary ; leafets of the 

 crown 2-toothed ; horn very short. 



Stony woods. Can. to Car. W. to Miss. June. %. — Stem 1— -2 feet high. 

 Leaves thin and membranaceous, the upper and lower ones opposite. Umbels 

 mostly 2, sometimes solitary, on long slender peduncles. Flowers small, white 

 or pale purple. • Four-leaved Sdkweed. 



b. Leaves alternate or verticillate. 



9. A. verlicillata Linn. ; stem simple, marked with pubescent lines ; 

 leaves mostly whorled, narrow-linear, revolute on the margin ; umbels ter- 

 minal and axillary ; leafets of the crown short, obtuse, 2-toothed ; horn 

 falcate, much exserted. 



Dry hills. Can. to Car. W. to Miss, and Texas. June — Sept. %.—Stem 

 1 — 3 feet high, very slender, often a little branched at the summit. Umbels 

 numerous, about an inch in diameter, terminal and subterminal. Flowers small, 

 greenish- white. Whorled Silkweed. 



10. A tuberosa Linn. : hairy ; stem erect, oblique or decumbent, with 

 spreading branches ; leaves oblong-lanceolate, linear-lanceolate or linear, 

 mostly alternate, subsessile; umbels numerous, often forming corymbs; 

 horn subulate, rather erect. A. decumbens Willd. 



Sandy fields. Can. to Car. W. to Miss. June — Aug. %. — Root large, tube- 

 rous. Stem 1 — 3 feet long. Leaves sometimes broad and cordate, at others 

 linear and somewhat tapering at base. Flowers large, in numerous erect umbels, 

 bright orange. Plant without milky juice. Medicinal. See Big. Med. Bot. ii. 59. 



BtOterfly Weed. Pleurisy Root. 



** Nectary or stamineal crown without horns. Acerates. Ell. 



11. il. viridijlora Raf,: stem erect or ascending, hairy; leaves oval, 

 ovate and obovate, on short petioles, tomentose-pubescent on both sides, ob- 

 tuse ; umbels subglobose, many-flowered, subsessile, nbdding ; pedicels to- 

 mentose. A' nutans MuU. A. lanceolata Ives. Acerales viridijlora and 

 obovata Ell. 



Sandy fields. Can. to Car. W. to Miss. July. %.— Stems 1—2 feet high, 

 sometimes clustered. Leaves 2 — 3 inches long, rather thick and coriaceous, 

 varying in form. Umbeh 2 — 4, subterminal, on short thick hairy peduncles. 

 Flowers green. I follow Decaisne, Torrey and Darlington, in uniting A. lanceo' 

 lata of Ives with this species. Green-flowered Silkweed. 



