Verbena xutha Lehm., coarse vervain, gulf vervain. Perennial herb, 1—several–stemmed at base, ascending, in range to 85 cm tall; shoots with cauline leaves; hispid–hirsute with the larger hairs having swollen bases (pustulate) and short glandular hairs with colorless heads.
Stems 4–sided, to 5 mm diameter, 2 sides flat and 2 somewhat rounded.
Leaves opposite decussate, mostly 3–lobed, sessile to subsessile, without stipules; blade deeply cut usually with a pair of opposite, minor lateral lobes within 20 mm of base, long–tapered at base, toothed on margins, acute at tip, pinnately veined with principal veins sunken on upper surface and conspicuously raised on lower surface.
Inflorescence spike, terminal and axillary in canopy, 50+–flowered, flowers helically alternate but subopposite at base, unevenly spaced along rachis, hispid–hirsute with the largest hairs pustulate, also with short glandular hairs; peduncle ridged, < 15 mm long; rachis ridged, with 1 ridge descending from each bractlet; bractlet subtending flower awl–shaped, ca. 4 mm long but not reaching tip of calyx, green, short–hirsute; bracteole subtending flower threadlike, ca. 1.5 mm long, colorless, short–hairy.
Flower bisexual, ± radial, ca. 7 mm across; calyx 5–lobed, ca. 3.5 mm long with free tips; tube keeled, 3 mm long, membranous with green ridges; corolla 5–lobed, ± trumpet–shaped but limb bent downward from perpendicular; tube ± cylindric, ca. 3 × 0.7—0.9 mm, white, glabrous on outer surface, with short radiating hairs inside from midpoint to top below filaments; throat lower portion 1.7—2 × 1.2 mm, light purple, having hairs on outer surface, upper portion broadly funnel–shaped, orifice blocked by a ring of stiff, pale lavender, inward–leaning hairs to 0.5 mm long concealing anthers and stigma; lobes subequal, widely spreading, truncate to inconspicuously or shallowly notched, 1.5—2 × 1.5—2 mm, light purple to lavender, having stiff short hairs on both surfaces; stamens 4, pairs attached to top of corolla tube at levels 1 mm and 0.6 mm below ring of hairs, included; filaments curved, 0.4 mm long, white; anthers dorsifixed, dithecal, 0.4 mm long, light yellow, longitudinally and inwardly dehiscent; pollen light yellow; nectary disc covering lower third of ovary, light green, nectar–producing; pistil 1, 2.2 mm long, included; ovary superior, shallowly 4–lobed, 0.8 × 0.4 mm, green, glabrous, ; style cylindric but flattened approaching top, 1.2—1.4 mm long, light green, glabrous, unequally 2–branched, terminal stigmatic branch hemispheric, colorless, flanked by short branch.
Fruit schizocarp (microbasarium), of 1—4 dry, 1–seeded mericarps (nutlets), mericarps oblong, 1.7—2 × 0.6—0.7 mm, satiny brown, rounded back with longitudinal ridges and depressions, fertile and undeveloped mericarps strongly coherent.
A. C. Gibson