Description

Key Characters:

Growth Form: Perennial herbs from a caudex or short rhizome.

Stems: Stems erect, decumbent, or occasionally prostrate, sometimes rooting at the nodes, 1–5 dm long, villous–puberulent, sometimes glabrate.

Roots:

Leaves: Leaves simple. Opposite. Blades lanceolate, elliptic, or ovate, 2–9 cm long, 0.7–4 cm wide. Apex acute. Base broadly cuneate to truncate. Surfaces sparsely scabrid. Margins subentire to remotely crenulate. Petioles usually 1–2 cm long. Stipules absent.

Flowers: Flowers in inflorescences 2–5 cm long, usually ca.1.5–2 cm in diameter, bracts suborbicular to very broadly ovate, usually 7–10 mm long, apex abruptly short-acuminate, margins ciliate. Calyx bilabiate, narrowly funnelform, green or purple, 7-10 mm long, irregularly 10–nerved, upper lip broad, shallowly 3-toothed, lower lip deeply cleft into 2 narrow teeth, splitting longitudinally, usually persistent or sometimes only ventral 1/2 persistent. Corolla zygomorphic, bilabiate, blue or violet, occasionally pink or white, 8-16 mm long, contracted at throat, tube often exserted beyond calyx, pilose, with a ring of hairs within, upper lip galeate, entire or subentire, lower lip shorter, 3-lobed, lateral lobes deflexed, median one concave, margins crenulate; nectary disk often present at base of ovary, annular or developed on anterior side only. Stamens 4, in 2 pairs, ascending under the galea, lower pair longer, scarcely exserted beyond corolla tube, aligned with the sinuses; anther sacs divaricate; anthers dithecal, on an expanded connective, opening by longitudinal slits. Ovary superior, 2-carpellate; ovules 1 per ovary lobe, placentation basal-axile; style 1; stigmas 2.

Fruit: Nutlets 1-seeded; brown; oblong-ovoid; glabrous; apex rounded; ca. 1.8 × 0.9 mm; slightly 1-furrowed. Seeds with endosperm absent or scanty and oily.

Ploidy: 2n = 14; 21; 28; 32; 42; 56

Habitat: naturalized in usually mesic; disturbed areas; especially pastures and along streambeds in wet forest.

Elevation Range: 820–2,260 m.