Vascular Plants of Williamson County

Dicliptera brachiata [Acanthaceae]
false mint

Dicliptera brachiata (Pursh) Spreng., false mint.  Perennial herb, 1—several–stemmed at base, suberect to ascending, to 70 cm tall; shoots with only cauline leaves, short–hairy, not aromatic.

Stems

Stems conspicuously 6–ridged, to 4 mm diameter, with 3 ridges descending from leaf, 6 ridges at each node, internodes to 75 mm long, hairy along ledges.

Leaves

Leaves opposite decussate, simple, petiolate with ledges across node, without stipules; petiole broadly channeled, to 25 × 1.5 mm, with colorless ridges, with long hairs on margins and lower side and short–hairy in channel; blade narrowly ovate, 15—55 × 8—20 mm, dull, tapered at base and often unequal, entire, obtuse to acute with short point at tip, pinnately veined with principal veins slightly raised on both surface, the longest hairs along veins and on margins.

Inflorescence

Inflorescence cyme, paired and axillary, each 2—several–flowered, bracteate; bract subtending cyme broadly elliptic, to 10 × 7 mm increasing 2× in fruit, fused across node and at base ca. 0.5 mm, hairs longer in fruit, with obovate lobes 2.6—3 mm wide, lobes 5–veined, green with narrow membranous margins below midpoint, rounded at tip with short point, inner (upper) surface glabrous and outer surface with short hairs along principal veins and scattered above midpoint; peduncle initially to 1 mm long increasing to 4 mm long in fruit, 6–ridged, short–strigose with downward–pointing hairs; bractlet subtending pedicel oblanceolate, ca. 3.5 × 1 mm, short–ciliate on margins above midpoint and with scattered short hairs; pedicel short, 0.4 mm long.

Flower

Flower bisexual, bilateral, 3.5—4.5 mm across × 10 mm (spreading lips), ca. 16 mm long; calyx 5–lobed, light green; tube 1 mm long; lobes acuminate–triangular, 2.5—3 × 0.5—0.6 mm increasing in fruit, 3–veined, papillate short–ciliate on margins, with short hairs; corolla 2–lipped; tube + throat ca. 7 mm long, white, tube glabrous, throat short–villous + several glandular hairs on sides; lips elliptic, 8.5—9 × 4—4.4 mm, mostly light purple, upper lip horizontal and lower lip diverging downward ca. 60°, upper lip with 3 short teeth, concolor with solid color, upper surface short–villous + glandular hairs; lower lip upper surface white at base with purple to dark purple spots approaching midpoint, light purple above midpoint, glabrous, lower surface pale purple, short–villous + glandular hairs; stamens 2, fused to sides of corolla 4—5 mm from base, exserted but < upper corolla lip; filaments ± straight, ca. 8 mm long, light purple, sparsely short–hairy and glandular–hairy; anthers dorsifixed, monothecal, 2 mm long, purple and white, longitudinally and downwardly dehiscent; pollen creamy white; nectary disc 2–lobed, appressed to base of ovary, 0.5 × 0.7—0.8 mm, green; pistil 1; ovary superior, narrowly ovoid, 1.1—1.3 × 0.7—0.8 mm, green, glabrous, 2–chambered, each chamber with 2 ovules; style 7.5—8 mm long, white, subequally 2–branched, the branches fingerlike, 0.25—0.3 mm long and stigmatic tip, with scattered short stiff hairs to midpoint.

Fruit

Fruit capsule, 2–valved, to 4–seeded in 2 chambers, explosively dehiscent, ovoid compressed ⊥ septum, greenish and membranous, short–hairy on capsule edges.

Seed

Seed disclike to waferlike, 1.6—2.1 × 1.6—2.1 × 0.5—0.7 mm, dark brown, flat surfaces low–bumpy, papillate along raphe.

A. C. Gibson