Polystemma cordifolium

(A. Gray) McDonnell & Fishbein

Phytologia 99: 86. 2017.

Common names: Sonoran milkweed vine
Illustrated
Basionym: Rothrockia cordifolia A. Gray Proc. Amer. Acad. Arts 20: 295. 1885
Synonyms: Matelea cordifolia (A. Gray) Woodson
Treatment appears in FNA Volume 14.

Stems: bark tan, corky, shal­lowly furrowed. Leaves: 1 stip­ular colleter on each side of pet­iole; petiole 1–4.5 cm; blade ovate, 2.5–8 × 2–6 cm, charta­ceous, base deeply cordate, laminar colleters 2–4, mar­gins planar, apex acute to acuminate, ven­ation pinni­palmate, surfaces densely puberulent to hirsute, paler abaxially. Inflorescences umbelliform or racemiform, 4–6-flowered; peduncle 1–4 cm. Pedicels 5–10 mm. Flowers: calyx lobes lanceolate-ovate, apices acute, 3–5 mm, hirsutulous; corolla tube 3–4 mm, lobes ascending, sometimes twisted, linear-lanceolate to oblong, 6–12 mm, glabrous; corona segments basally connate and united to base of column, green, laminar, fleshy, ovate with minute teeth, much shorter than gynostegium; gynostegium sessile; style apex prolonged into bifid beak, papillose. Follicles 4.5–13.2 × 1–1.5 cm, apically attenuate. Seeds 100–150, reddish brown, 6 × 4 mm, granulate-tuberculate; coma white, 3–4 cm.


Phenology: Flowering Jul–Sep; fruiting Oct–Mar.
Habitat: Arroyos, can­yons, hills, slopes, plains, rock outcrops, granite, sandy and gravelly soils, desert scrub.
Elevation: 200–300 m.

Distribution

Ariz., Mexico (Baja California, Baja California Sur, Sonora).

Discussion

Polystemma cordifolium is widely distributed in the drier parts of the Sonoran Desert and reaches its northern limit in Organ Pipe Cactus National Monument (Pima County), where it may no longer be extant (R. S. Felger et al. 2014). It should be considered to be of conservation concern in the flora area.

Selected References

None.

Lower Taxa

None.
... more about "Polystemma cordifolium"
Mark Fishbein +  and Angela McDonnell +
(A. Gray) McDonnell & Fishbein +
Rothrockia cordifolia +
Sonoran milkweed vine +
Ariz. +, Mexico (Baja California +, Baja California Sur +  and Sonora). +
200–300 m. +
Arroyos, canyons, hills, slopes, plains, rock outcrops, granite, sandy and gravelly soils, desert scrub. +
Flowering Jul–Sep +  and fruiting Oct–Mar. +
Illustrated +
Matelea cordifolia +
Polystemma cordifolium +
Polystemma +
species +