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 6. Callitriche dacryoidea Lansdown & Hassemer , sp. nov. Type: — BOLIVIA . LA PAZ: Hierba acuática con raíces en el fondo de la laguna, desvío 11 km hacia Laguna Hampaturi , 10 km hacia Los Yungas , Murillo Province , 1 May 1980 , S.G. Beck 2944 ( holotype NY!) . Diagnosis: — Callitriche dacryoidea has very striking fruit which are black when mature, unwinged and wider at the base than the apex. These characters serve to distinguish it from all other Callitriche species. Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves unknown, expanded submerged or floating leaves elliptic, 1.8–3.4 × 1.4–1.8 mm , petiole 1.6–2.0 mm, venation complex and unusual with two points from which secondary veins arise on central nerve, the apical leaves forming a floating rosette, leaves of terrestrial plants unknown. Bracts persistent, 0.7 mm long. StYle persistent, 1.0– 1.4 mm long. Filament erect, caducous, ≤ 1 mm long; anther size unknown, pollen yellow. Fruit not strumose, sessile, longer than high, black when mature, widest near base, 1.4–1.6 × 1.2–1.4 mm , unwinged. Illustrations: — Figure 1 (g). Distribution: —This species is known only from the holotype from Hampaturi Lake in Yungas Province of Bolivia . There are no altitude data available. Etymology: —The specific epithet means tear-or pear-shaped and refers to the unique shape of mature fruit. Notes: — Callitriche dacryoidea is known from a single gathering ( S.G. Beck 2944 ), and no duplicates of the holotype could be located. It resembles C. heteropoda , but differs in the shape and colour of mature fruit. Conservation status: —Available information is inadequate to derive an informed assessment of the conservation status of C. dacryoidea and it is therefore classed as Data Deficient (DD).