Osmoxylon ngardokense Costion, 2016

Costion, Craig M. & Plunkett, Gregory M., 2016, A revision of the genus Osmoxylon (Araliaceae) in Palau, including two new species, PhytoKeys 58, pp. 49-64 : 51-54

Osmoxylon ngardokense Costion sp. nov. Fig. 2

Type.

Palau. Melekeok: Ngardok forest dynamics plot, 07°30'36.97"N, 134°36'28.04"E, 50 m, 17 Jul 2014 (fr.) C. Costion 3721 (holotype: NY; isotype: BNM, US).

Description.

Small understory tree, 7-10 m tall, unbranched. Leaf blades large with distinct celery smell when crushed, up to 60 cm long and 75 cm wide, with 9-11 lobes; margin weakly serrated, serrations exserted or protruding from margin and spaced far apart, generally 1 per secondary vein or up to one between secondary veins; prominent secondary veins 8-13 per lobe, meeting the mid-rib at a near 90°(perpen dicular) angle then curving to a 30-45°angle; petioles up to 92 cm in length; petiolar crests 3, circular, with papery edge and minutely toothed; stipule 3.5-4 cm long, deeply furrowed, slightly appressed to stem and mildly recurved on the axial side, tip not sharp or firm. Inflorescence 20-25 cm in diameter, primary axis bearing 30-40 secondary inflorescence units, secondary axis (from primary axis to where lateral umbellules are attached) c. 3.5 cm long, sterile fruits not seen; lateral peduncles jointed, c. 4-5 cm long, bottom segment 1.2-1.5 cm, top segment 2.5 cm; dark purplish-black in color. Fertile flowers 20-30 per umbellule, with light-green, fused or united, globose to cup-shaped calyx, 2-2.5 mm long; corolla tube bright yellow-orange, 4-5 lobed, 3 mm long, 1.5-2mm wide; stamens alternate to the petal lobes, partially exserted; ovary inferior, greenish, stigmas sessile. Fruits 30-40 per umbellule, with 5 locules (each 1-seeded), globose, 3-6 mm in diameter, turning dark blackish-crimson; fruiting umbellules globose, 2-2.5 cm in diameter at maturity, spaced apart, not densely packed.

Notes.

Osmoxylon ngardokense is so far known only from the type locality, with volcanic soil, near Lake Ngardok on Babeldaob, within the Ngardok Nature Reserve, for which the species is named. This species is clearly distinct from the other Palau taxa of Osmoxylon by its large 9-11 lobed leaves, large compound inflorescence with inflorescences widely spaced, and dark crimson globose fruits in globose clusters of 30-40.

Specimens examined.

Palau. Melekeok State: Ngardok Nature Reserve in Ngardok forest dynamics plot, 21 Jul 2014, 23 Jul 2014, C. Costion 3895 (BNM), C. Costion 3725 (NY).

Figures

Figure 2. Osmoxylon ngardokense a compound inflorescence b inflorescence c inflorescence with mature fruits d inflorescences fruiting and flowering e flower head up close f mature fruits up close g petiolar stipule h petiole crests i leaf.