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).