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Published In: Species Plantarum 1: 212. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/3/2009)


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2. Cynanchum L.

Plants with clear latex and thus watery sap (milky or yellow latex elsewhere). Stems twining, usually climbing, branched or unbranched. Leaves opposite, short- to long-petiolate. Leaf blades narrowly to broadly ovate or triangular-ovate, the base rounded, truncate, or cordate, the tip tapered to a sharp point, the margins flat or somewhat wavy, sometimes slightly curled under. Inflorescences solitary in the leaf axils, mostly relatively short-stalked, consisting of sometimes branched or slightly racemose, umbellate clusters. Calyces with the lobes spreading or loosely ascending at maturity, narrowly triangular or lanceolate to ovate, sparsely short-hairy on the outer surface. Corollas erect or ascending at flowering, white to cream-colored or dark purple to nearly black. Gynostegium appearing sessile or nearly so, the corona as long as or usually longer than the anther/stigma head, modified into 5 erect, lateral, petaloid segments or a shallow, cuplike, fleshy disk. Fruits pendant, narrowly elliptic-lanceolate to ovate in outline, circular or slightly flattened in cross-section (not angled), the surface smooth, glabrous or short-hairy. Seeds strongly flattened and narrowly winged, brown to dark brown, with a tuft of long, white, silky hairs at the tip. Two hundred to 400 or more species, nearly worldwide, mostly in tropical and warm-temperate regions.

Generic limits and the circumscriptions and relationships among subgroups in the Cynanchum alliance are among the most poorly understood in the Asclepiadaceae. Rosatti (1989) noted that because previous authors included so many species with exceptions to the morphological character states used to define most of the subgroups, comparisons of different classifications have been nearly impossible. Liede (1997) and her colleagues have been studying the infrageneric classification of the genus and its segregates for a number of years, but this classification should still be viewed as preliminary and not fully resolved. The two species present in Missouri have very different coronal structures and probably are not closely related. The North American Ampelamus group contains only the species treated here as Cynanchum laeve, a relatively isolated taxon whose relationships are not well understood (Sundell, 1981; Liede, 1996, 1997). Cynanchum louiseae is part of the Vincetoxicum group, a relatively cohesive segregate that comprises up to 100 or more Old World species (Liede, 1996), of which 3 have become introduced in temperate North America as escapes from cultivation (Sheeley and Raynal, 1996). It is likely that ongoing molecular studies will result in the breakup of Cynanchum in the broad sense into a number of smaller genera, but until further data become available in the literature it seems premature at the present time to recognize more than a single polymorphic genus.


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1 1. Corollas white to light cream-colored; leaf blades deeply cordate at the base ... 1. C. LAEVE

Cynanchum laeve
2 1. Corollas dark purple to nearly black; leaf blades rounded, truncate, or shallowly cordate at the base ... 2. C. LOUISEAE Cynanchum louiseae
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