Hydriastele, Wendland & Drude, 1875

Petoe, Peter, Heatubun, Charlie D. & Baker, William J., 2018, A monograph of Hydriastele (Areceae, Arecaceae) in New Guinea and Australia, Phytotaxa 370 (1), pp. 448-450 : 448-450

Key to Hydriastele in New Guinea and Australia

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Solitary or clustering, slender, understorey to midstorey palms; stem diam. <10 cm (rarely up to 15 cm); leaf <2.5m long, leaflets ≤40 each side of rachis.......................................................................................................................................................................2 Solitary, robust, subcanopy to emergent palms; stem diam.> 10 cm; leaf> 1.5 m long (usually> 2.5 m), leaflets ≥40 each side of rachis (rarely as few as 38 per side).................................................................................................................................................18 Leaf blade irregularly pinnate............................................................................................................................................................3 Leaf blade regularly pinnate or entire-bifid......................................................................................................................................10 Inflorescence protandrous, spicate or branched to 1 or 2 orders; pistillate petals with pronounced pointed apex; fruit with a distinct, dark, sclerotic zone encircling apical stigmatic remains (ca. 1.5–5 mm in diam.)............................................................................4 Inflorescence protogynous, branched to 1 or 2 orders; pistillate petals rounded; fruit with inconspicuous stigmatic remains lacking encircling dark sclerotic zone.............................................................................................................................................................9 Leaf typically with 3 broad, multi-fold leaflets each side of rachis interspersed with a few single-fold leaflets; pistillate sepals fused in a cup and petals fused basally (Biak Islands).................................................................................................... H. dransfieldii (14) Leaf not consisting of broad, multi-fold leaflets interspersed with single-fold leaflets; pistillate sepals and petals only fused briefly at the very base (New Guinea)...........................................................................................................................................................5 Palm up to 25 m tall; leaflets 27–40 each side of rachis (rarely as few as 21 per side); leaf sheath conspicuously fibrous at apex; inflorescence branched to 2 orders (New Guinea) ........................................................................................................ H. lurida (13) Palm up to 10 m tall; leaflets 2–23 each side of rachis; leaf sheath not conspicuously fibrous at apex; inflorescence spicate or branched to 1 order.............................................................................................................................................................................6 Leaflets 15–23 each side of rachis, concavely praemorse at their tips; triads decussately arranged (Sandaun Province, Papua New Guinea) .......................................................................................................................................................................... H. aprica (12) Leaflets 2–13 each side of rachis, never concavely praemorse at their tips; triads spirally arranged................................................7 Stem 1.5–7.5 cm in diam. (rarely as slender as 0.8 cm in diam.); inflorescence 18–30 cm long (rarely as short as 13 cm), with 2–6 rachillae; endosperm ruminate (New Guinea)........................................................................................... H. pinangoides (6; in part) Stem 1–2 cm in diam.; inflorescence 8–15 cm long, spicate or with 2 rachillae (rarely with 3 rachillae in cultivation); endosperm ruminate or homogeneous..................................................................................................................................................................8 Basal and middle leaflets narrowly linear and divaricate, i.e. appearing to be extending nearly perpendicular to the leaf rachis; endosperm ruminate (Papua Province, western New Guinea) .................................................................................. H. divaricata (9) Leaflets variable in size and shape but never narrowly linear and not divaricate; endosperm homogeneous (New Guinea) ............. ..................................................................................................................................................................... H. flabellata (10; in part) Slender clustering palm; leaf sheath 15–30 cm long; leaflets 6–13 each side of rachis; endosperm ruminate ( Bismarck Archipelago) ............................................................................................................................................................................ H. kasesa (2) Slender or moderate, solitary or clustering palm; leaf sheath 40–73 cm long; leaflets 12–30 each side of rachis; endosperm homogeneous to ruminate (New Guinea and Australia).................................................................................. H. wendlandiana (1; in part) 10.

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