The genus Callitriche (Plantaginaceae: Callitricheae) in South America Author Lansdown, Richard V. 0000-0003-0984-4552 Ardeola Environmental Services, 45 The Bridle, Stroud, Gloucestershire, GL 5 4 SQ, United Kingdom & Honorary Research Associate, Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, United Kingdom & r. lansdown @ kew. org; https: // orcid. org / 0000 - 0003 - 0984 - 4552 r.lansdown@kew.org Author Hassemer, Gustavo 0000-0003-4365-6934 Câmpus de Três Lagoas, Universidade Federal do Mato Grosso do Sul, CEP 79613 - 000, Três Lagoas, MS, Brazil & g. hassemer @ ufms. br; https: // orcid. org / 0000 - 0003 - 4365 - 6934 g.hassemer@ufms.br text Phytotaxa 2021 2021-05-19 501 1 85 118 http://dx.doi.org/10.11646/phytotaxa.501.1.3 journal article 10.11646/phytotaxa.501.1.3 1179-3163 5424744 14. Callitriche nubigena Fassett (1951: 191 , t. 1174[17]). Type: — COLOMBIA . SANTANDER : pool on páramo, Alto del Almorzadero , north of Cerrito , 12000 ft , 12 October 1944 , N.C. Fassett 25918 ( holotype MO!; isotypes CM, GH barcode 00048935!, NY!, US-2166224 barcode 00095627!, WIS!) . Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves 7.5–18.2 × 0.3–0.7 mm , expanded submerged or floating leaves 2.5–3.2 × 1.5–2.6 mm , petiole 2.0– 3.7 mm , venation simple or with a few short looped or anastomosing veins, apical leaves forming a floating rosette, leaves of terrestrial plants unknown. ♂ and ♀ flowers in the same aXil, tYpicallY opposed bY a solitarY ♀ . Bracts persistent, 0.7–2.0 mm StYle erect ≤ 2.0. Filament erect, 0.6–2.9 mm ; anther 0.3–0.4 mm diameter; pollen yellow. Fruit not strumose, subsessile, ± as wide as high, black when mature 0.7–1.2 × 0.7–1.2 mm in diameter, winged throughout but wider at apex 0.03–0.07 at apex, 0.01–0.04 mm on side. Illustrations: —plate 1174(17) in Fassett (1951) ; Figure 5 (c). FIGURE 6. Holotype of Callitriche mandonis ( G. Mandon 1456 , BR barcode AWH12906680). Copyright: Plantentuin Meise. Distribution: —This species is endemic to Colombia where it is known from a small region east of La Belleza, Santander Province , north of Bogotá ( Fassett 1951 , specimens in F, GH, USNC). Records from other areas (e.g. Antioquia , Bolívar and Cundinamarca in Colombia , Ancash in Peru and Mérida in Venezuela ) ( Luteyn 1999 , Hokche et al. 2008 , Idárraga-Piedrahita et al. 2011 , Missouri Botanical Garden 2014) are based on mis-identifications. Known altitudinal range: 110– 800 m . See map on page 173 in Fassett (1951) . Notes: —Both known specimens of this species were collected by N.C. Fassett, who also named the species. As noted by Fassett (1951) the two collections have fruit of different sizes, that from the Paramo had fruit 0.9–1.2 mm (mis-represented by Fassett as 9–12 mm ) high and wide, while that from the oxbow had fruit 0.7–0.8 mm high and wide ( Fassett 1951 ). There is clearly a need to collect more material from the two known localities, as well as surveying in the region to try to find more populations, to establish whether this fruit size variation is genetic or whether the species is simply very variable. Callitriche nubigena can be distinguished from other Callitriche species by the fruit which are sessile and narrowly winged, with ♀ and ♂ flowers in most aXils, the bracts persistent and> 1.5 mm long, and the stYles> 2 mm long. It is most similar to C. albomarginata , from which it can be distinguished by its smaller fruit and large, persistent bracts. Conservation status: — Callitriche nubigena is classed as Data Deficient (DD) as it is known from only two gatherings made in 1944, from a fairly restricted area of Colombia . Additional material studied: — COLOMBIA . SANTANDER : Aquatic form in 20 cm . water, pool in pasture, “Moravia,” a level valley north-east of La Belleza , valley of Rio Minero near Florian , 7000 ft. , September 26, 1944 , N.C. Fassett 25808 (GH, MO, US [not listed by Fassett]); subaquatic form, N.C. Fassett 25809 (GH, MO); terrestrial form on mud, N.C. Fassett 25807 (GH, MO); small shallow pool, half-way between Sucre and La Belleza , 7650 ft. , September 25, 1944 , N.C. Fassett 25796 (CM, F [not listed by Fassett ], UC, US ,, WIS) .