The genus Callitriche (Plantaginaceae, Callitricheae) in Australasia and Oceania Author Lansdown, Richard V. Ardeola Environmental Services, 45 The Bridle, Stroud, Gloucestershire, UK. GL 5 4 SQ. & Honorary Research Associate, Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE text Phytotaxa 2022 2022-05-24 547 3 243 284 journal article 56760 10.11646/phytotaxa.547.3.3 deb1c3fa-44cf-4574-9b18-ec5c9881e6c5 1179-3163 6577535 15. Callitriche papuana Merrill & Perry (1941: 258) . Type: — INDONESIA . WEST PAPUA . Submerged (green) aquatic rooting in outer shallows of Lake Habbema , 3225m , Aug. 1938 , L . J . Brass 9541 ( Holotype : A; isotypes K 110073869!, L 950278395) . Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves very long and narrow, 0.7–22.0 mm long × 0.4–0.5 mm wide; expanded submerged or floating leaves narrowly elliptic, 4.4–5.5 mm long × 1.6–2.3 mm wide; venation simple or occasionally branched with veins between central and secondary veins, petiole 3.2–6.5 mm long; leaves of terrestrial plants unknown. Flowers solitary. Bracts strongly falcate, caducous, 1.5–1.8 mm long. Styles erect or sub-divergent 2.3–8.0 mm long. Filament erect 3.8–5.5 mm long; anthers, 0.5 mm long × 0.6–0.7 mm wide, number of locules unknown; pollen yellow. Fruits subsessile or very shortly pedicellate, as high as or slightly higher than wide, blackish when mature, 1.4–1.6 mm long × 1.2–1.4 mm wide, narrowly winged throughout. Illustrations: — Fig. 10e . Recognition: — C. papuana can be distinguished from all other Callitriche species in the region by the fruit which are narrowly winged, higher than wide and blackish when mature, combined with the solitary flowers and large bracts. Fruits of C. aucklandica may be considered similar but are typically wider than high, while its vegetative parts are typically fleshy. Distribution: —Native. Callitriche papuana is known from a few specimens collected in the highlands of New Guinea , from Lake Habbema in West Papua, to Mount Victoria near Port Moresby in New Guinea ( Fig. 14 ). Habitats and Ecology: — C. papuana has been described as occurring in water with pH between 6.50 and 7.50, including in the shallow, marginal waters of a lake surrounded by forest. Populations determined as C. palustris , but probably this species have been reported from pools, the outflow stream from a lake and a small bog lake at high altitude, with a thick growth of submerged Isolepis fluitans (von Linné) R.Br. (1810: 221) and Spirogyra Link (1820: 5) , surrounded by fringe of Carex gaudichaudiana Kunth (1837: 417) fen which is surrounded in turn by Carpha alpina fen ( Hoogland 1958 , Wade and McVean 1969 ). 2225–4100 m elevation. Conservation Status: —The information available is not adequate to assess the conservation status of the species and it is therefore classed as Data Deficient ( IUCN 2012 ). Notes: — C. papuana is extremely poorly known, with no records since 1980. As with many other Callitriche species in the region, there is a need for fieldwork to assess its current conservation status and collect accurate information on its distribution. FIGURE 14 . The distribution of confirmed specimens of C. papuana Selected specimens examined: — INDONESIA : WEST PAPUA : Lake Habbema , 3225m alt., August 1938 , L.J. Brass 9541 (K) . PAPUA NEW GUINEA . Lake Aunde , 23 January 1976 , Verdcourt 4909 (P 04214987); Salawaket 3 April 1937 , M.S. Clemens 5733 ( GH ) ; Morobe , 6 April 1940 , M.S. Clemens 41125 ( GH ) ; Mt. Wilhelm , 17 June 1959 , L.J. Brass 29986 ( CANB 102003 , GH , NY , US ) ; Murray Pass , Wharton Range , June-Sept. 1933, L.J. Brass 4774 ( NY ) ; Mt. Victoria , 5 July 1974 , J. Croft et al. LAE 61654 ( BRI AQ329318 ) ; Mt. Edward , 20 June 1974 , J. Croft et al. LAE 61334 ( BRI AQ329329 ) ; Lake Aunde , 15 September 1971 , N.M. Wace ANU13042 ( CANB 765114.1 , CANB 230517 ) ; Mt. Wilhelm , 1965, M.M.J.v. Balgooy 186 ( CANB 321839 ) ; Mt. Giluwe , 22 September 1961 , R. Pullen 2882 ( CANB 98477 ) ; Kongdarumbun , 1 October 1964 , R.D. Hoogland 9971 ( CANB 150082 ) ; Mt. Wilhelm , July 1969 , G. Hope ANU10804 ( CANB 241288 ) ; Mt. Giluwe , 15 August 1972 , P.F. Stevens & D.B. Foreman LAE 52252 ( CANB 282972 ) ; Mt. Wilhelm , 16 June 1967 , L.K. Wade ANU 7771 ( CANB 173944 ) .