Vascular Plants of Williamson County

Erythranthe glabrata [Phrymaceae/Scrophulariaceae]
roundleaf monkeyflower

Erythranthe glabrata (Kunth) G. L. Nesom (syn. Mimulus glabratus var. glabratus), roundleaf monkeyflower. Aquatic perennial herb, sometimes with short stolons, fibrous–rooted, not rosetted, often mat–forming and procumbent with flowering shoots ascending to erect, mostly < 15—65 cm tall; shoots with only cauline leaves, shoots often with purplish red leaves and stems, appearing glabrous with widely scattered stalked glandular hairs mostly along petioles or near blade margins; adventitious roots at submerged and lower nodes of procumbent stems.


Stems initially 6–angled aging cylindric, to 7 mm diameter, long internodes to 90 mm long, and hollow.


Leaves opposite decussate, simple, petiolate fused across node, without stipules; petiole channeled and somewhat winged, 2.5—25 mm long, green to purplish, with several stalked glandular hairs on fused margins and approaching blade; blade broadly ovate or somewhat deltate, 12—35 × 13—48 mm, truncate to subcordate or cordate at base, dentate on margins with minor teeth on shoulders, obtuse to broadly acute at tip, palmately veined with principal veins sunken on upper surface and raised on lower surface, glabrous.


Inflorescence ± leafy raceme or panicle of lateral racemes from base, terminal, raceme > 5–flowered, having pair of axillary flowers at each node, bracteate, glabrous; bractlet subtending pedicel, in pairs at node, leaflike, the uppermost ones subsessile, ; pedicels ascending to spreading, slender, at anthesis ca. 5—6 mm long increasing in fruit, often purplish and glaucous, with stalked glandular hairs.


Flower bisexual, bilateral, ca. 8 mm across; calyx 5–lobed, 6—7 mm long increasing in fruit, strongly 5–pleated; tube bell–shaped and pleated, 5 × 3 mm, green with purple–red spots, edges, and margins, pleat to each lobe, glabrous; lobes toothlike, < 1 mm long but the lowest lobe ± 2 mm long, glandular short–ciliate on sinus margins; corolla 2–limbed, 5–lobed, 12—14 mm long; tube cylindric somewhat flaring, ca. 3 × 3.5 mm, 2.5 mm diameter at base, white, glabrous; throat narrowly funnel–shaped, 6—8 mm long, ca. 5 mm across at orifice, outer surface yellowish to yellow at orifice and glabrous, inner surface red–dotted on floor (dots < 20), short–pilose on ceiling and next to stamens, infolded (invaginated) on lower side to form a densely hairy palate of 3 broad ridges expanding toward orifice separated by a groove extending into lower lip, the hairs narrowly club–shaped and yellow; lips bright yellow, glabrous, upper lip 2–lobed, ca. 4 mm long, the lobes curved backward, semicircular, ca. 1.5 × 2.8—3.2 mm; lower lip with a pair of spreading, semicircular lateral lobes, 2 × 3 mm and a central lobe with 2 semicircular sublobes 1.5 × 5 mm. stamens 5, fused to corolla, 1 pair arising ca. 2 mm and other pair 3 mm from base of corolla; filaments ca. 4 mm long (upper stamens) and ca. 5 mm long (lower stamens), white; anthers dorsifixed, dithecal, ± 0.8 mm long, pale yellow to yellowish white, longitudinally dehiscent; pollen yellow; nectary disc below ovary, ± 0.35 × 1 mm diameter, green; pistil 1, 6—7 mm long, short–stalked (stipe); ovary superior, compressed ellipsoid, 2.5—3 × 1—1.3 mm, light green, glabrous, 2–chambered, each chamber with many ovules attached to center; style cylindric with constriction at base, 3.5—4 mm long, white (pale green), flared at top, 2–branched, the branches = unequal, stigmatic flaps, on upper (inner) surfaces conspicuously papillate, yellowish.


Fruit capsule, loculicidal, short–stalked, dehiscent, 2–valved, many–seeded, ellipsoid and somewhat compressed, mostly 7—9.5 × 3.5—4.5 mm, shallowly grooved along septum, narrowly ridged along line of dehiscence, glabrous, with persistent style; calyx concealing capsule, to 12 mm long, 5–pleated.


Seed elliptic to oblong, 0.4—0.5 × 0.2—0.3 mm, golden brown, longitudinally ridged to slightly netlike, the ridges minutely sinusoidal and commonly discontinuous.

A. C. Gibson