Bacopa verticillata (Pennell & Gleason) Pennell (1946: 92)

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 : 19-22

12. Bacopa verticillata (Pennell & Gleason) Pennell (1946: 92) . Fig. 12 .

≡ Caconapea verticillata Pennell & Gleason (1929: 403) .

Type:— BRAZIL. “Extreme northern Brazil south of Mount Roraima ”, 21 Sep 1927, O. Tate 72 (holotype NY 00067936!, isotype PH 00010109!).

= Bacopa pedersenii Rossow (1986: 176) .

Type:— ARGENTINA. Corrientes. Mburucuyá, Santa Teresa, Quebrachal, Cañada Fragosa. 26 Dec 1980, T. M. Pedersen 12980 (lectotype CTES 0013901! [designated here], isolectotypes BR 0000005423767!, CTES 0013902!, G 00356531!, S 04-3412!, UPS V-708427!).

Herbs, annual, 20 cm tall, prostrate stems, slightly puberulous. Leaves 3 – 5 verticillate, sessile, dimorphic: submerged leaves with blade pinnatisect or pinnatifid, aerial leaves with blade pinnatifid to entire, margin entire to serrate, 7 – 16 × 1 – 3 mm, apex acute or obtuse, base amplexicaul or auriculate, glabrous on both surfaces. Flowers axillary, solitary, sessile or with brief pedicels 0.5 mm long, bracteoles two, linear, 1 – 2 mm long, glabrous. Calyx 5-lobed, the two external dorsal lobe ovate, 2.5–3 × 1.5 – 2 mm, apex rounded, base truncate, lateral lobes ovate, 3.2–3.8 × 1.8–2 mm, apex acute, base truncate, glabrous; two internal lobes linear, 1.8–2 × 0.8–1 mm, apex acute, glabrous or with glandular hairs. Corolla white, or pale blue color, tube 3–4 mm long, glabrous; stamens 4; ovary glabrous, style entire, stigmatic; apex bilobed. Capsule globose, apex rounded, 2.5–2.8 × 2.4–2.5 mm.

Distribution and habitat:—Native species from South America, distributed from Guyanas and Venezuela to northeastern Argentina in the province of Corrientes. It is found on humid, sometimes submerged terrain.

Nomenclatural remarks:— Rossow (1986) clearly indicated that the type collection is housed at CTES. However, two sheets were found there, thus the specimen showing the best quality of preservation of the important diagnostic features of the taxon is here chosen as lectotype of the name (Art. 9.17).

Taxonomic remarks:— Bacopa verticillata is easily distinguished being the only Argentine Bacopa with 3 – 5 verticillate leaves with pinnatisect or pinnatifid blades (being opposite leaves with entire blades in the rest of the species).

Selected specimens examined:— Corrientes: San Miguel, Ea. San Juan Poriajhu, ruta 17, Tressens 4277 (CTES, LIL).

Figures

FIGURE 12. Bacopa verticillata. A. Plant aspect. B. Plant with submerged and aerial leaves. C. Detail of node with aerial leaves. D. Detail of node with submerged leaves and flowers. E. Detail of node with submerged leaves. F. Flower with internal lobes. G. Corolla opened, showing stamens. H. Calyx and gynoecium. I. Dorsal lobe, internal view. J & K. Lateral lobes, internal views. L & M. Internal lobes. N. Capsule (A–H, N, from Wood & Huaylla 20745, LPB, Bolivia, Dpto. Santa Cruz, Velazco, camino entre el Refugio hacia los Fierros, 14° 34’S, 61° 01’ W, 18 Apr 2004; I–M, from Pedersen 12980, CTES, lectotype Bacopa pedersenii).