29. Gonolobus Michaux, Fl. Bor.-Amer. 1: 119. 1803.
[Greek gonia, angle, and lobos, pod, alluding to follicle shape]
Alexander Krings
Vincetoxicum Walter, Fl. Carol., 13, 104. 1788, not Wolf 1776
Vines, herbaceous [woody], perennial; latex white, rarely clear. Stems twining, unarmed, eglandular-pubescent or mixed eglandular- and glandular-pubescent. Leaves deciduous [persistent], opposite, petiolate; stipular colleters 2, 1 borne at base of petiole on each side, interpetiolar colleters absent [present], infrapetiolar colleters absent; laminar colleters present. Inflorescences extra-axillary, racemiform [paniculiform, umbelliform], pedunculate. Flowers: calycine colleters present [absent]; corolla white, light yellow, uniformly green, olive-green, yellow-green, or neon green or multicolored and generally dark maroon or brownish near base and green to yellow-green near tips, rotate, aestivation dextrorse; corolline corona ± annular, sometimes interrupted and developed only in staminal [rarely interstaminal] position, or absent; androecium and gynoecium united into a gynostegium adnate to corolla tube; gynostegial corona of fused staminal and interstaminal segments, lobed [unlobed]; anthers adnate to style, dorsal appendage laminar, locules 2; pollen in each theca massed into rigid, horizontally oriented pollinium, pollinia strongly curved, bearing sterile, navicular portion adjacent to translator, pollinia of adjacent anthers joined by translators to common corpusculum together forming pollinarium. Fruits follicles, solitary or paired, moderately to strongly deflexed, green to brown, ovoid, 5-angled, occasionally fewer-angled, smooth to tuberculate, glabrous or pubescent. Seeds obovate, flattened, winged, not beaked, comose, not arillate. x = 11.
Species 100–150 (3 in the flora): United States, Mexico, West Indies, Central America, South America; introduced in Africa.
The indumentum in Gonolobus can consist of trichomes of uniform length but more often includes a mixture of long eglandular, short eglandular, and/or short glandular capitate trichomes. Stems, petioles, peduncles, and pedicels may have indumentum in lines or completely around the stalk (ubiquitous).
SELECTED REFERENCES Krings, A. 2008. Synopsis of Gonolobus s.l. (Apocynaceae, Asclepiadoideae) in the United States and its territories, including lectotypification of Lachnostoma arizonicum. Harvard Pap. Bot. 13: 209–218. Krings, A., D. T. Thomas, and Xiang Q.-Y. 2008. On the generic circumscription of Gonolobus (Apocynaceae, Asclepiadoideae): Evidence from molecules and morphology. Syst. Bot. 33: 403–415.
