Stachytarpheta angustifolia (Mill.) Vahl, Enum. Pl. 1: 205. 1804; Verbena angustifolia Mill.
Hierbas erectas de menos de 1 m de alto, tallos glabros excepto en los nudos. Hojas lineares, 7.5–11 cm de largo (incluyendo al pecíolo) y 0.5–1.2 cm de ancho, ápice y base atenuados, margen distalmente remotely serrado, haz densely and minutely scabrous- puberulent, the trichomes often not visible at 20x, but rough to the touch, also sometimes with pocos larger tricomas dispersos, envés con tricomas en los nervios. Inflorescencia 12–40 cm de largo y 3–5 mm de ancho, glabra, brácteas ovadas, 5–7 mm de largo y 1.5–2 mm de ancho, aristadas, margin very minutely serrulate; cáliz 5–7 mm de largo, minutely scabrous-puberulent, sometimes with slightly longer trichomes on the margins of the lobes, apically 2-lobado, the lobes entire or weakly bifid, sin dientes observables or central longitudinal ribs; corola azul o morada. Fruto 4 mm de largo.
Rare, aguas quietas y sabanas; Río San Juan y Chontales; 40--325 m; fl ago; Miller 1358, Stevens 30675; México a Costa Rica, norte de Sudamérica y en las Antillas.
Some authors (Hammel and Grayum, 2011; Fernandes, 1984) have placed Stachtarpheta angustifolia in synonymy with S. indica (L.) Vahl, while Moldenke (1983) informally suggested S. angustifolia as a variety of S. indica. Atkins (1985), while rejecting the lectotypification of V. indica, considered this specimen to be equivalent to S. angusitfolia. However, even a casual examination of the lectotype of Verbena indica (Herb. Linn. No. 35.2, larger branch on right of sheet) suggests that it does not represent true S. angustifolia. It has the lower leaves broadly lanceolate and the lateral veins at ca. 45° angle to the midrib while the type of the basionym of S. angustifolia (Verbena angustifolia), in additional to all the material I have seen of this taxon from Mexico and Central America, has all the leaves linear or very narrowly oblong, with the lateral veins at ca 20° angle to midrib.
H. N. Moldenke and A. L. Moldenke. Verbenaceae. In: M. D. Dassanayake (ed.). A Revised Handbook to the Flora of Ceylon 4: 196—487. 1983; R. B. Fernandes. Notes sur les Verbenaceae I-Remarques sur quelques espèces de Stachytarpheta Vahl. Bol. Soc. Bot., sér. 2, 57: 87—111. 1984; S. Atkins. The genus Stachytarpheta (Verbenaceae) in Brazil. Kew Bull. 161—272. 2005.