Bacopa dubia Chodat & Hassler (1904: 290)

Sosa, María De Las Mercedes, Moroni, Pablo & O’Leary, Nataly, 2018, A taxonomic revision of the genus Bacopa (Gratioleae, Plantaginaceae) in Argentina, Phytotaxa 336 (1), pp. 1-27 : 6

3. Bacopa dubia Chodat & Hassler (1904: 290) . Fig. 3 .

Type:— PARAGUAY. In palude Tapangua, Oct, E. Hassler 3309 (lectotype G 00307148! [designated here], isolectotypes BM 000953363!, G 00307156!, G00307158!, MPU 020755!, S-04-3405!).

Herbs, annual 7–10(–20) cm tall, prostrate, stems flexuous, slightly strigose. Leaves opposite, sessile, blade ovate, 6–10 × 4–6 mm, apex rounded, base rounded, margin entire, abaxial surface puberulous on the veins. Flowers axillary, solitary, pedicels 40–50 mm long, slightly strigose, bracteoles absent. Calyx 5-lobed, the external dorsal lobe wide ovate, 5.5–6 × 3.8–4 mm, apex rounded, base cordate, the two lateral lobes ovate, 4.8–5 × 2.8–3.2 mm, apex acute, base cordate, slightly puberulous, the two internal lobes linear, 4.8–5 × 1.5–1.8 mm, apex acute, puberulous. Corolla white, tube 8–12 mm long, glabrous; stamens 4; ovary glabrous, style bifid, stigmatic apex globose or smooth. Capsule ovoid, apex acute, 2.8–3 × 1.8–2 mm.

Distribution and habitat:—Native to South America, it is found in Paraguay and northeastern Argentina, in the provinces of Corrientes and Misiones. It grows between sea level and 500 m elev.

Nomenclatural remarks:—In describing B. dubia Chodat & Hassler (1904) cited five collections from Paraguay in the protologue. Since no holotype was indicated they are all syntypes (Arts. 9.3, 9.5). In spite of the fact that all the collections are totally in agreement with the protologue, the syntype Hassler 6161 is preferred over the other elements since it is the most plentiful and best preserved. Thus, one of the specimens belonging to this collection is here selected as lectotype of the name.

Taxonomic remarks:— Bacopa dubia is similar to B. australis (see remarks under this last species).

Selected specimens examined:— Corrientes: San Cosme, ruta 12, límite con dpto. Itatí, 28 Nov 1981, Krapovickas et al. 37552 (BAB, CTES, LIL). Misiones: Capital, Bañado Arroyo Zaimán, 15 Sep 1995, Guillén & Lirussi 460 (CTES).

Figures

FIGURE 3. Bacopa dubia. A. Plant aspect. B. Calyx. C. Corolla opened, showing stamens. D. Gynoecium. E. Detail of two stamens. F. Calyx with dorsal lobe opened. G. Dorsal lobe, external view. H & I. Lateral lobes, external views. J & K. Internal lobes (from Arbo 598, CTES).