1. Trachelospermum difforme (Walter) A. Gray (climbing dogbane)

Echites difformis Walter

Pl. 216 a–e; Map 900

Plants lianas or sometimes appearing herbaceous, sometimes more or less emergent aquatics. Stems 2–5 m or more, woody or mostly herbaceous, twining, often rooting at the nodes, glabrous or with sparse, short, reddish hairs, especially when young. Leaves opposite, the petioles 4–5 mm long. Leaf blades 2.5–9.0 cm long, 0.5–5.5 cm wide, variable in shape from broadly ovate or nearly circular to lanceolate or narrowly oblong-elliptic, narrowed or more commonly tapered to a sharply pointed tip, angled, tapered, or rarely rounded at the base, the upper surface glabrous and sometimes somewhat shiny, the undersurface sparsely to densely short-hairy. Inflorescences axillary, loose clusters or small panicles. Calyces glabrous or sparsely hairy, the lobes 2.5–3.0 mm long, narrowly ovate-triangular. Corollas funnelform to trumpet-shaped, lacking appendages, the tube 5–7 mm long, the lobes 1.5–2.0 mm long, yellow with red coloration on the inner surface toward the top of the tube and the lobes, sparsely hairy inside the tube. Stamens attached near the midpoint of the corolla tube, the anthers incurved and adhering to the stigma, appearing arrowhead-shaped with a pair of slender basal lobes. Nectar glands 5, positioned around the ovary bases alternating with the stamens. Style elongate, the stigma appearing somewhat umbrella-shaped with a broadly club-shaped body that is expanded into a basal wing. Fruits 10–23 cm long, usually pendulous, slender, reddish, dehiscing along the longitudinal suture. Seeds 0.8–11 mm long, truncate to tapered at the base, the tip with a dense tuft of yellowish gray hairs 14–15 mm long. June–July.

Uncommon in the Mississippi Lowlands Division and southern portion of the Ozarks north locally to Iron County (southeastern U.S. west to Missouri, Oklahoma, and Texas). Bottomland forests, swamps, banks of streams and rivers, oxbows, and rarely glades; also ditches and roadsides.

The leaves of T. difforme are quite variable, ranging from broadly ovate or nearly circular to narrowly oblong-elliptic or lanceolate. Some specimens have both broad and narrow leaves on the same plant, sometimes on the same branch. The leaves generally are evergreen farther south, but in Missouri are frequently deciduous, and the aboveground portions often die back partially or completely during especially cold winters.

Woodson (1935) and Steyermark (1963) reported a record of T. difforme from St. Louis County, but although Woodson himself apparently collected this specimen in 1931 along the margins of Creve Coeur Lake, it could not be located during the present study. The existence of this New World taxon may be due to the ancient biogeographic connection between eastern Asia and eastern North America. Alternatively, T. difforme may be more closely related the tropical American genus Secondatia than to the Asiatic species. Woodson (1935) suggested that the distribution of T. difforme matches the ancient continental shorelines of the Cretaceous Period, much like that of Taxodium distichum (bald cypress).