Vincetoxicum nigrum
Vincetoxicum rossicum
black swallow-wort
dog-strangling vine, dompte-venin de russie, pale swallow-wort
erect to prostrate proximally, twining distally.
erect proximally, twining distally.
petiole 0.5–1.5 cm;
blade pinnipalmately veined, lanceolate to broadly ovate, 3–12 × 1–6.5 cm, membranous, base truncate, rounded, or subcordate, with 2–8 laminar colleters, margins ciliate, apex attenuate to acuminate, surfaces pilosulous on veins abaxially, glabrous adaxially.
petiole 0.5–2 cm;
blade pinnipalmately veined, elliptic or lanceolate to ovate, 6.5–12 × 2.5–7 cm, membranous, base truncate to rounded, with 2–8 laminar colleters, margins ciliate, apex acuminate, surfaces pilosulous on veins abaxially, glabrous adaxially.
solitary at nodes, simple or compound cymes, 4–10-flowered;
peduncle 0.5–1.5 cm, pilosulous.
solitary at nodes, simple or compound cymes, 5–20-flowered;
peduncle 1.5–2.5 cm, pilosulous in a single line.
5–6 mm, pilosulous.
3–7 mm, pilosulous.
calyx lobes lanceolate to deltate, 1–1.5 mm, apex acute, pilosulous to glabrate, margins ciliate;
corolla very dark purple, rotate to rotate-campanulate, fleshy, lobes apically planar, deltate, 1.5–3 mm, ± as wide as long, apex acute, glabrous abaxially, pilosulous to hispidulous adaxially, gynostegial corona a thick, shallowly 5-lobed or crenulate ring exceeding style apex, reddish purple to dark purple;
style apex depressed, umbonate, green.
calyx lobes narrowly lanceolate, 2 mm, apex attenuate, glabrous;
corollas pinkish tan to reddish brown, campanulate, not fleshy, lobes spreading, apically twisted, lanceolate, 3–5 mm, 1.5–2 times longer than wide, apex obtuse to acute, glabrous, gynostegial corona of 5 prismatic, basally united segments exceeding style apex, pinkish tan to brick red;
style apex depressed, umbonate, green.
7–15, brown, ovate, 6–8 × 3–4.5 mm;
coma white, 2–3 cm.
10–20, brown, lenticular, lanceolate to ovate, 4–6.5 × 2.5–3 mm;
coma white, 2–3 cm.
4–8 × 0.7–1 cm, apex attenuate to acuminate.
3.5–7 × 0.5–0.6 cm, apex attenuate to acuminate.
= 44.
= 22.
Vincetoxicum nigrum
Vincetoxicum rossicum
Vincetoxicum nigrum is more widely known in North America by the illegitimate name Cynanchum nigrum (Linnaeus) Persoon, a later homonym of C. nigrum Cavanilles [basionym of the Mesoamerican species Gonolobus niger (Cavanilles) R. Brown ex Schultes]. It is the more frequently encountered and better established of the two Vincetoxicum species in the United States. One of the earliest and best documented escapes from cultivation occurred in Cambridge, Massachusetts, where garden plantings at Harvard University (when Asa Gray was herbarium director in the late 1800s) and elsewhere were documented as serving as invasion foci for surrounding areas. The species is still commonly encountered on fences in many places in Cambridge. In addition to the states listed above, V. nigrum is known from cultivation near Minneapolis, Minnesota, but is not yet known to have escaped in that state. Chromosome numbers of 2n = 22 and 2n = 44 have been reported from the native range in Europe, and it is unclear whether the introduced populations are exclusively tetraploid or also include diploids (A. DiTomasso et al. 2005). Unlike most species of Apocynaceae that have been studied, V. nigrum has been shown to be capable of autogamous pollination through the in situ germination of pollinia within anther thecae (DiTomasso et al.).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The taxonomy of Vincetoxicum rossicum in the flora area has long been confused, as described above. This species has been reported from North America as V. hirundinaria (Cynanchum vincetoxicum) and V. medium (C. medium). Vincetoxicum hirundinaria is cultivated in the flora area and may persist ephemerally but appears not to have naturalized. Vincetoxicum rossicum has not always been distinguished from V. hirundinaria. Thus, early reports of C. vincetoxicum or V. hirundinaria mostly apply to V. rossicum. Even when the two species were distinguished, plants of V. rossicum were commonly called C. medium or V. medium; however, this name is now considered misapplied to V. rossicum and to be a synonym of V. hirundinaria. There have been numerous reports of V. hirundinaria in the northern United States and southern Canada, but the great majority of these have been shown to represent V. rossicum, either through examination of herbarium specimens or interpretation of descriptions of corolla color.
Vincetoxicum rossicum is the more frequently encountered and better established species of the genus in Canada. In addition to the provinces listed above, V. rossicum is known from cultivation near Halifax, Nova Scotia, but is not yet known to have escaped in that province. Like V. nigrum, V. rossicum has been shown to be facultatively autogamous, via in situ pollinia germination, a rare condition in Apocynaceae (A. DiTomasso et al. 2005).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
IL Wildflowers
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