Bacopa rotundifolia (Michx.) Wettstein (1895: 76)

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 : 14-16

8. Bacopa rotundifolia (Michx.) Wettstein (1895: 76) . Fig. 8 .

≡ Monniera rotundifolia Michaux (1803: 22) ≡ Herpestis rotundifolia (Michx.) Pursh (1813: 418) nom. illeg., hom. non Gaertner (1807: 186) ≡ Macuillamia rotundifolia (Michx.) Rafinesque (1840: 44) ≡ Ranapalus rotundifolius (Michx.) Pennell (1920: 242) .

Type:— UNITED STATES OF AMERICA. Illinois, État de l’Illinois, dans les marais, May 1849, A. Trécul 742 (neotype P 03535493! [designated here], isoneotypes P 03535482!, P 03535499!).

= Herpestis tweedii Bentham (1846: 397) ≡ Monniera tweedii (Benth.) Kuntze (1891: 463) ≡ Bacopa tweedie (Benth.) Parodi (1930: 240) .

Type:— ARGENTINA. Córdoba, J. Tweedie s.n. (lectotype K!, two sheets [first-step designated by Souza & Giulietti 2009: 48], second-step lectotype K 000373794! [designated here], isolectotype K 000533445!).

= Bacopa limosa (Pennell) Standley (1925: 460) ≡ Macuillamia limosa Pennell (1920: 158) .

Type:— COLOMBIA. Cundinamarca, Melgar, Dec 1917, F.W. Pennell 2927 (holotype NY 00090653!, isotypes CAS 0003270!, PH 00016463!, US 00122518!).

= Bacopa simulans Fernald (1942: 438) .

Type:— UNITED STATES OF AMERICA. Virginia, Charles City County, sandy-muddy fresh tidal shore of Chichahominy River, Graves Landing, north of Holderoft, Sep 10 1941, M. L. Fernald & B. H. Long 13749 (lectotype GH 00077923! [designated here], isolectotypes BM 001025113!, BRIT 23358!, F 0072297F!, GH 00077924!, K 000979484!, MICH 1109980!, NY00067865!, US 00036890!, WIS v0256278!).

= Bacopa nobsiana Mason (1952: 206) .

Type:— UNITED STATES OF AMERICA. California, rice fields, Sutter bypass, just south of Marysville, Sutter County, Jul 29, 1949, M. Nobs & S. G. Smith 1097 (holotype UC 927650!, isotypes CAS 0027916!, K 000979488!, NY 00067864!)

Herbs, annual, 20–30 cm tall, prostrate, sub-glabrous or slightly strigose. Leaves opposite, sessile, blade orbicular, 10–14 × 10–13 mm, apex obtuse, base rounded, margin entire, glabrous. Flowers axillary, solitary, pedicels 5–10 mm long, sub-glabrous or slightly puberulous, bracteoles absent. Calyx 5-lobed, the external dorsal lobe wide ovate, 3.8–4.2 × 2.5–3 mm, apex rounded, base cordate or rounded, the two lateral lobes oblong, 3.8–4.2 × 1.8–2.2 mm, apex acute or obtuse, base truncate, glabrous, the two internal lobes linear, 3.8–4.2 × 1.4–1.6 mm, apex acute, glabrous. Corolla white, tube 4.5–5 mm long, glabrous; stamens 4; ovary glabrous, style bifid, stigmatic apex globose. Capsule ovoid, apex rounded, 2.8–3 × 1.8–2 mm.

Distribution and habitat:— Bacopa rotundifolia is a species of wide geographic distribution, occurring from southern United States of America to northern Argentina. It grows between sea level and 500 m elev.

Nomenclatural remarks:— Michaux (1803) described Monniera rotundifolia based on a specimen collected by him in Illinois, USA. Michaux’s herbarium is kept at P, separate as l’herbier historique ( Stafleu & Cowan 1981) but there is no material associated with this name there. However, a specimen annotated by Michaux as M. rotundifolia (P [barcode] 03535496 [digital image!]) was traced in the general herbarium of P. Even though Michaux studied this specimen, there is no evidence concerning the place of collection or date of herborization, therefore this material cannot be considered as original material. For this reason, the specimen Trécul 742 is here selected as a neotype since it shows all the morphological features described in the protologue.

Souza & Giulietti (2009) designated as lectotype of Herpestis tweedii a specimen housed at K. There are, however, two sheets associated with this name and these authors did not distinguish between them. Thus Souza & Giulietti’s designation is here considered as a first-step typification (Art. 9.17). This designation is here narrowed by selecting the most complete specimen as a second-step lectotype.

Although Fernald (1942) clearly indicated the herbarium which houses the type collection of Bacopa simulans , two sheets were found at GH. 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 rotundifolia could be confused with B. dubia , being both small annual herbs, prostrate, sub-glabrous or slightly strigose, with absence of bracteoles. They are distinguished because B. dubia has slightly puberulous calyx lobes, vs. glabrous in B. rotundifolia .

Selected specimens examined:— Chaco: Primero de Mayo, Col. Benítez, Jan 1934, Schulz 859 (CTES). Corrientes: Bella Vista, ruta 117, 11 Mar 1976, Ahumada 311 (CTES). Formosa: Patiño, Bartolomé de las Casas, Apr 1971, Schulz 658 (CTES). Salta: Anta, Forestal, 17 Feb 1988, Saravia Toledo 1595 (CTES).

Figures

FIGURE 8. Bacopa rotundifolia. A. Plant aspect. B. Detail of node. C. Flower. D. Corolla opened, showing stamens. E. Open calyx showing fruiting gynoecium. F. Dorsal lobe, external view. G & H. Lateral lobes, external views. I & J. Internal lobes (from Ahumada 2002, CTES).