This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial herbs, similar to Asclcpias, with alternate or opposite thick leaves, and green or purplish flowers in terminal or axillary and short-peduncled or sessile umbels. Caly.x 5-parted or 5-divided, the segments acute, glandular within. Corolla deeply 5-cleft, the segments valvate, reflexed in anthesis. Corona-column very short. Corona of 5 involute-concave 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 solitary in each sac, oblong, pendulous. Stigma 5-lobed. [Greek, without horn, referring to the crown.]
About 7 species, natives of North America. Type species: Acerates longifolia (Michx.) Ell.
Umbels sessile, or very nearly so, mostly axillary. Leaves oval to linear: hoods entire at the apex.
1. A. viridiflora.
Leaves narrowly linear; hoods 3-toothed.
2. A. angustifolia.
Umbels, at least the lower, distinctly peduncled.
Plants glabrous, or nearly so; umbels usually several; leaves narrow. Hoods obtuse, entire; column 1/2" long; stem roughish puberulent.
3. A. ftoridana.
Hoods emarginate; column very short; stem glabrous.
4. A. auriculata.
Plant hirsute; umbel solitary, terminal; leaves- ovate to oblong.
5. A. lanuginosa.
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, 1°-3° high. Leaves slightly rough, alternate or opposite, thick, oval, oblong or ovate to lanceolate or linear, 1'-5' long, \'-2' wide, short-petioled, the margins usually undulate; umbels several, or rarely solitary, axillary, 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; anther-wings tapering below, semi-rhomboid above; follicles puberulent, 2'- 4' long.
In dry, sandy or rocky soil, Massachusetts to southern Ontario, Saskatchewan, Florida and Texas. Consists of several races, differing mainly in leaf-form. June-Sept.
Stems mostly several together, erect, straight, 1°-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-peduncled or subsessile, axillary, usually numerous; pedicels puberulent; corolla-segments oblong, greenish; hoods white, not exceeding the anthers, 3-toothed at the apex, the acute middle tooth merely a prolongation of the thickened crest-like midvein, shorter than the obtuse lateral ones; anther-wings notched at about the middle; follicles slender, erect, about 3' long or more.
On dry plains, Missouri, Nebraska and Colorado to Texas.