Callitriche oblongicarpa Fassett (1951: 194

Lansdown, Richard V. & Hassemer, Gustavo, 2021, The genus Callitriche (Plantaginaceae: Callitricheae) in South America, Phytotaxa 501 (1), pp. 85-118 : 106

15. Callitriche oblongicarpa Fassett (1951: 194 , t. 1174[20])

Type: — ARGENTINA. BUENOS AIRES: La Plata , 20 October 1928, L.R. Parodi 8571 (holotype GH barcode 00048936!) .

Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves unknown, expanded submerged or floating leaves spathulate, elliptic, 2.0–2.5 × 1.3–1.7 mm, petiole 3.2–5.0 mm, 3-veined, venation simple, venation complex with subsidiary veins arising within and outside the secondary veins forming loops, linking primary and secondary veins or anastomosing, the apical leaves forming a floating rosette, leaves of terrestrial plants unknown. Flowers solitarY or ♂ and up to 3 ♀♀ in a single aXil. Bracts persistent, 0.3–0.9 mm. StYle erect, ≤ 1.7 mm. Filament erect, ≤ 2 mm, maY arise from pedicel; anther 0.3 mm diameter; pollen Yellow. Fruit not strumose, subsessile or on pedicel <11 mm, as wide as high or higher than wide, sometimes tapering toward base, maroon to orange when mature, 0.7–0.9 × 0.70–0.95 mm, narrowly winged throughout.

Illustrations: —plate 1174(20) in Fassett (1951); Figure 5 (d).

Distribution: — Callitriche oblongicarpa is known from a small number of confirmed specimens, from Uruguay, Corrientes Province in Argentina and a single collection from Bolivia. See map on page 193 in Fassett (1951). There are no altitude data available.

Notes: — Callitriche oblongicarpa differs from all other Callitriche species by the combination of multiple male and female flowers in the same leaf axils and the long-pedicellate, very narrowly-winged fruit. The species was erroneously synonymised under C. lechleri by Bacigalupo (1979b), who overlooked the taxonomic importance of the long pedicels, a character that does not present a continuous variation linking C. lechleri to C. oblongicarpa . Extensive study of herbarium materials shows that the two species are undoubtedly distinct, hence our re-establishment of C. oblongicarpa .

Callitriche oblongicarpa is one of the most distinctive members of the genus due to its striking orange-brown pedicellate fruit. It is therefore surprising that Bacigalupo (1975) included it within her concept of C. lechleri . C. oblongicarpa is also very unusual in often having more than 2 female flowers in a single axil. Most collections are from Argentina, theY have abundant fruit with ≤ 3♀ fruit in a single aXil, some of which are long-pedicellate. In contrast, a single collection from Tierra del Fuego (A. Schinini 7362) is verY different; all fruit have short pedicels (≤ 1 mm) and are solitary. It is possible that these differences have a genetic basis, but this can only be clarified through study of fresh material, preferably supported by molecular analysis .

Conservation status: —Available information is inadequate to derive an informed assessment of the conservation status of C. oblongicarpa and it is therefore classed as Data Deficient (DD).

Additional material studied: — ARGENTINA. CORRIENTES: Estancia “Santa María”, Mburucayá Department, 4 September 1956, T.M. Pedersen 3976 (BR, C, G, K, NY, P barcode P04214918); flotante en charco, bosque de quebracho, Ruta 5, 18 km SE de San Luis del Palmar, Dep. San Luis de Palmar, 28 September 1975, C.L. Cristóbal 1266 (barcode G00414836); En charco, en bosque rebereño, sobre la laguna Iberá, Paso Picada, orilla de Laguna Iberá, frente a C. Pellegrini, Mercedes Department, 22 September 1973, A. Schinini 7362 (G, SI-065652). BOLIVIA. LA PAZ: Hierba acuatica con raices en el fondo de la laguna, desvio 11 km hacia laguna Hampaturi, 10 km hacia Los Yungas, Murillo Province , 1 May 1980, S.G. Beck 2944 (NY) [mixed with holotype of C. dacryoidea ]. URUGUAY. LAVALLEJA: En un charco an la [..] del [..] natante, Arequita , Uruguay , 3 October 1937, Rosengurt 1353 (F) .

Figures

FIGURE 5. Fruits of South American Callitriche: a—C. lechleri, b—C. mandonis, c—C. nubigena, d—C. oblongicarpa, e—C. praetermissa, f—C. quindiensis, g—C. rimosa, h—C. schotsmaniana, i—C. stagnalis, j—C. terrestris, k—C. turfosa.