PLANT: Perennial herbs or subshrubs, with vegetative parts more or less conspicuously hairy and frequently glandular. STEMS: twining or prostrate to strictly erect. LEAVES: opposite, in ours petiolate, ovate to lanceolate and mostly cordate at the base. INFLORESCENCE: 1- to several-flowered racemose, umbelliform, or irregular cymes, mostly sequentially blooming. FLOWERS: showy to rather small; corolla rotate to campanulate, mostly dull colored in shades of white, green, yellow or purple; crown extremely variable, in ours arising near the region of union of the corolla and filaments and more or less concealed by the corolla, ring- or cup-shaped and variously undulate to lobed or of 5 distinct, dorsiventrally flat to somewhat infolded segments opposite the anthers; anther head in ours subsessile or the column to 2 mm high, mostly disk- to funnel-shaped, the anther wings more or less curving down beneath the anther head; pollinia horizontal or less typically pendulous from the translator arms, with a sterile, hyaline area at the junction with the arm; stigma head flat to variously beaked. FOLLICLES: smooth, winged, or warty. NOTES: Ca 250 spp.; in warm temperate and tropical regions of N. and S. Amer. A taxonomically little-studied group exhibiting varied and perplexing elaborations of the crown, corolla, and stigma head, and often divided into several dozen segregate genera. REFERENCES: Sundell, Eric. 1994. Asclepiadaceae. J. Ariz. - Nev. Acad. Sci. Volume 27, 169-187.