14 



ASCLEPIADACEAE. 



[Vol.. III. 



A. viridiflora. 

 A. angustifolia. 



A. Floridana. 

 A. auriculata. 

 A. lanuginosa. 



(Fig. 2924.) 



3. ACERATES Ell. Bot. S. C. & Ga. 1: 316. 1817. 



Perennial herbs, similar to Asclepias, with alternate or opposite thick leaves, and green 

 or purplish flowers in terminal or axillary and short-peduncled or sessile umbels. Calyx 

 5-parted or 5-divided, the segments acute, glandular within. Corolla deeply 5-cleft, the seg- 

 ments valvate, reflexed in anthesis. Corona-column very short. Corona of 5 involute-con- 

 cave or somewhat pitcher-shaped hoods, neither horned nor crested within or in one species 

 having a small interior crest and usually a few small processes at the base of the anther- 

 wings, forming an obscure inner crown. Pollen-masses solitaiy in each sac, oblong, pendu- 

 lous. Stigma 5-lobed. [Greek, without horn, referring to the crown.] 



About 7 species, natives of North America. 

 Umbels sessile, or very nearly so, mostly axillary. 



Leaves oval to linear; hoods entire at the apex. i. 



Leaves narrowly linear; hoods 3-toothed. 2. 



Umbels, at least the lower, distinctly peduncled. 



Plants glabrous, or nearly so; umbels usually several; leaves narrow. 



Hoods obtuse, entire; column J4" long; stem roughish puberulent. 3. 

 Hoods emarginate; column very shoit; stem glabrous. 4. 



Plant hirsute; umbel solitary, terminal; leaves ovate to oblong. 5. 



i. Acerates viridiflora (Raf.) Eaton. Green Milkweed. 



Asclepias viridiflora Raf. Med. Rep. (II.) 5:360. 1808. 

 Acerates viridiflora Eaton, Man. Ed. 5, 90. 1829. 



Puberulent or tomentulose, at least when young; 

 stems simple, reclined or ascending, rather stiff, 

 i-3 high. Leaves slightly rough, alternate or 

 opposite, thick, oval, oblong or ovate, l'-jf long, 

 ^ / -2 / wide, short-petioled, the margins usually 

 undulate; umbels several, or rarely solitary, axil- 

 lary, densely many-flowered, sessile or very nearly 

 so; pedicels very slender, tomentose, 4 // -8 // long; 

 flowers green; corolla-segments narrowly oblong, 

 2 //- 3 // long; column very short or none; hoods 

 lanceolate-oblong, obtuse, minutely 2-auricled at 

 the base; mass of anthers longer than thick; an- 

 ther-wings tapering below, semi-rhomboid above; 

 follicles puberulent, i'-a/ long. 



In dry, sandy or rocky soil, Massachusetts to south- 

 ern Ontario and the Northwest Territory, south to 

 Florida and Texas. June-Sept. 



A. viridiflora Ivesii Britton, Mem. Torr. Club, 5: 265. 1894. 

 Asclepias lanceolata Ive. c , Am. Journ. Sci. 1: 252. 



1819. Not Walt. 1788. 

 Acerates viridiflora var. lanceolata A. Gray, Syn. Fl. 



2: Part 1, 99. 1878. 

 Leaves lanceolate or oblong-lanceolate, 2' -5' long, Vf'-i" wide. Range of the type, often with it. 



Acerates viridiflora linearis A. Gray, Syn. Fl. 2: Part. 1, 99. 1878. 

 Leaves elongated-linear; stem low; umbels often solitary. Minnesota and Manitoba to the 

 Northwest Territory, Louisiana and New Mexico. 



2. Acerates angustifolia (Nutt.) Dec. 

 Narrow-leaved Milkweed. (Fig. 2925.) 



Polyolus angustifolius Nutt. Trans. Am. Phil. Soc. 



(II.) 5: 201. 1833-37. 

 A. angustifolia Dec. in DC. Prodr. 8: 522. 1844. 

 Asclepias stenophylla A. Gray, Proc. Am. Acad. 12: 



72. 1876. 



Stems mostly several together, erect, straight, 

 i-2 high, puberulent above, glabrate below. 

 Leaves opposite, or some of the lower alternate, 

 sessile, narrowly linear, 2 / ~5 / long, glabrous, the 

 revolute margins and the thick midvein rough 

 beneath; umbels 10-15-flowered, short-pedun- 

 cled or subsessile, axillary, usually numerous; 

 pedicels puberulent; corolla-segments oblong, 

 greenish; hoods white, not exceeding the an- 

 thers, 3-toothed at the apex, the acute middle 

 tooth merely a prolongation of the thickened 

 crest-like midvein, shorter than the obtuse lat- 

 eral ones; anther-wings notched at about the mid- 

 dle; follicles slender, erect, about 3' long or more. 



On dry plains, Nebraska and Colorado to Texas. 



