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star milkvine, two flower matelea, two-flower milkvine

Habit Herbs.
Stems

4–10, decumbent, often branched near base, 7–40 cm, hirsute with long eglandular and minute glandular trichomes.

Leaves

1 or 2 colleters on each side of petiole;

petiole 0.5–2.5 cm, hirsute with long eglandular and minute glandular trichomes;

blade ovate to deltate, 0.8–5 × 0.6–3.2 cm, base shallowly to deeply cordate, with 0–2 laminar colleters, apex acute (rounded), surfaces hirsute with long eglandular and minute glandular trichomes, especially so on veins abaxially.

Inflorescences

solitary, umbelliform, extra-axillary, sessile or subsessile, 1–2-flowered.

Pedicels

3–11 mm, hirsute with long eglandular and minute glandular trichomes.

Flowers

calyx lobes spreading, oval to ovate, 1.8–2.5 mm, apex rounded or acute, hirsute with long eglandular and minute glandular trichomes;

corolla maroon to dark brown, not reticulate, rotate-campanulate, tube 1–1.5 mm, lobes spreading, ovate to narrowly deltate to spatulate, 3–6 mm, margins usually reflexed, pilose to hirsute adaxially;

corona united to corolla and column near base, composed of 5 united segments forming a ring at base, each with an adaxial incurved appendage arching above or incumbent on anthers, equaling or exceeding style apex, maroon to dark brown, 1–1.5 mm, glabrous;

apical anther appendages white, maroon to brown at base, broadly deltoid;

style apex rounded, flat.

Seeds

tan to light brown, oval to nearly orbicular or ovate, 8–11 × 7–10 mm, margins broadly winged, chalazal end erose, faces minutely rugose;

coma 2.5–4 cm.

Follicles

not striate, ellipsoid to ovoid, 4.5–8.5 × 1.8–3.5 cm, apex acute, densely muricate (more than 1 protrusion per cm of length), villous to hirsute with long eglandular and minute glandular trichomes.

Matelea biflora

Phenology Flowering Mar–Oct; fruiting Apr–Dec.
Habitat Calcareous prairies, hillsides, pastures, fields, savannas.
Elevation 100–1300 m. (300–4300 ft.)
Distribution
from FNA
NM; OK; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Matelea biflora is occasionally found in grasslands and savannas of the southern Great Plains. It is most common on and around the Edwards Plateau of central Texas, where it occurs in grass-dominated habitats including disturbed areas. The range extends mostly northward and westward of that region to central Oklahoma and extreme eastern New Mexico (Lea County), where the species is much less common. Its conservation status in New Mexico merits evaluation. The plants are covered in short, glandular hairs and are malodorous when touched. The flowers occur most often in pairs, hence the common name two-flowered milkvine.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 14.
Parent taxa Apocynaceae > Matelea
Sibling taxa
M. alabamensis, M. atrostellata, M. baldwyniana, M. brevicoronata, M. carolinensis, M. chihuahuensis, M. cynanchoides, M. decipiens, M. edwardsensis, M. flavidula, M. floridana, M. hirtelliflora, M. obliqua, M. parviflora, M. parvifolia, M. producta, M. pubiflora, M. radiata, M. reticulata, M. sagittifolia, M. texensis
Synonyms Gonolobus biflorus, Chthamalia biflora, G. biflorus var. wrightii
Name authority (Rafinesque) Woodson: Ann. Missouri Bot. Gard. 28: 228. (1941)
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