A monograph of Hydriastele (Areceae, Arecaceae) in New Guinea and Australia Author Petoe, Peter Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, United Kingdom. Author Heatubun, Charlie D. Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, United Kingdom. & Fakultas Kehutanan, Universitas Papua, Jl. Gunung Salju, Amban, Manokwari 98314, Papua Barat, Indonesia. & Badan Penelitian dan Pengembangan Daerah Provinsi Papua Barat, Jl. Brig. Jend. Mar. (Purn.) Abraham O. Atururi, Arfai, Manokwari 98315, Papua Barat, Indonesia. * author for correspondence, w. baker @ kew. org w.baker@kew.org Author Baker, William J. Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, United Kingdom. text Phytotaxa 2018 2018-09-24 370 1 448 450 http://dx.doi.org/10.11646/phytotaxa.370.1.1 journal article 10.11646/phytotaxa.370.1.1 1179-3163 13705467 9. Hydriastele divaricata Heatubun, Petoe & W.J. Baker (2018: 18) . Type :— INDONESIA . Papua Province : Mimika Regency (Previously Fakfak Regency), Timika, PT . Freeport Indonesia Area of Work , Mile 39, 100 m , 4°20’S , 136°58’E , 23 February 1998 , Baker et al. 876 ( holotype K!, isotypes BH!, BO!, L!, MAN!) Clustering, very slender understorey palm forming clumps of ca. 5 stems, to 4.5 m tall. Stem ca. 9–17 mm in diam. Leaf ca. 80 cm long including petiole; sheath ca. 25 cm long; petiole ca. 27–30 cm long; leaflets 8–12 per side, irregularly to subregularly arranged, divaricate in the basal and middle portion of the leaf, single- or bi-fold, narrowly linear, praemorse apically. Inflorescence 10–12 cm long including 2–2.5 cm peduncle, spicate or branched to 1 order, protandrous; rachillae 1–2; triads spirally arranged. Staminate flower not seen. Pistillate flower 4–4.5 × 3–3.3 mm at early fruiting stage, with free sepals and free petals with conspicuous, triangular tips. Fruit ca. 12 × 3 mm when ripe, cylindrical, pale green to pinkish, with a distinct, dark, sclerotic zone encircling apical stigmatic remains (up to ca. 2 mm in diam.). Seed ca. 8 × 2 mm , elongate to cylindrical; endosperm shallowly ruminate. Distribution:— Known only from the type locality on the lower slopes of the Mt. Jaya region ( Dransfield et al. 2000 ) near to Timika in Papua Province, western New Guinea . Habitat:— The transition zone between lowland alluvial rain forest and heath forest, 100 m . Uses:— None recorded. Vernacular names:— None recorded. Conservation status:— Data deficient (DD; Heatubun et al. 2018 ). Specimens examined:— INDONESIA . Papua Province : Mimika Regency (Previously Fakfak Regency), Timika, PT . Freeport Indonesia Area of Work , Mile 39, 100 m , 4°20’S , 136°58’E , 23 February 1998 , Baker et al. 876 (BH!, BO!, K!, L!, MAN!) . Notes:— Hydriastele divaricata is a very slender understorey palm distinguished by its narrowly linear leaflets, which are widely spreading (divaricate) in the basal and middle section of the leaf. The limited available material displays inflorescences consisting of just one (spicate) or two rachillae, prompting comparison with H. flabellata and H. montana , but these two species have homogeneous endosperm whereas H. divaricata has ruminate endosperm. Hydriastele divaricata is described in more detail by Heatubun et al. (2018) .