Osmoxylon leidichii 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

Osmoxylon leidichii Costion sp. nov. Fig. 1

Boerlagiodendron pachyphyllum Kaneh. p.p., Bot. Mag. Tokyo, 48: 401, 1934

Osmoxylon leidichii Syntype: Palau. Aimeliik: 1933, R. Kanehira 2452

Type.

Palau. Koror: Ngeremdiu Beach, 07°15'20.22"N, 134°26'37.98"E, 18m, 6 Jun 2014 (fr), C. Costion 3711 (holotype: NY; isotype: US, BNM).

Description.

Small to medium sized tree, 10-12 m tall, branched. Leaf blades palmately lobed, up to 45 cm long and wide, glabrous, with 7-9 rhombic lobes; margin with serrations minute and distinctly inserted or in tiny indentations of the blade, barely exceeding the margin itself, only one per secondary vein; prominent secondary veins 7 or 8 per lobe, meeting the mid-rib at a 30-45°angle; petioles up to 50 cm in length; petiolar crests 1-4, circular, re-curved, entire, with tannish pubescence along margins; stipule flattened and appressed to the stem, broadly attenuate to the apex, fleshy (not stiff), with brown flakey or papery margins and brownish pubescence, tip soft to touch, not firm. Inflorescence 10-15 cm in diameter, primary axis bearing 20-30 secondary inflorescence units, secondary axis (from primary axis to the point where the lateral fertile umbellules are attached) c. 2 cm long, with c. 30 pinkish to crimson, baccate pseudo-fruits, each 2 mm long and 2-3 mm in diameter; peduncles c. 3 cm long, light green, not distinctly jointed. Fertile flowers 10-20 per umbellule, each with a yellowish, fused or united, cup-shaped calyx, c. 2 mm long; corolla tube bright orange, 5 or 6 lobed, 3 mm long; stamens alternate to the petal lobes, strongly exserted; ovary inferior, whitish-green, stigmas sessile. Fruits 10-20 per umbellule, each with 5 or 6 locules (each 1-seeded), globose-ovoid, 7-8 mm long, 6-7 mm in diameter, turning white (when immature) then maturing to pale pink, tightly clustered at maturity, forming a distinct hemispheric or mound-shaped infructescence.

Notes.

Osmoxylon leidichii occurs across the limestone islands of Palau on karst and coral substrates and within this range it appears to be common. It has been previously confused with Osmoxylon pachyphyllum , but is distinguished by its 7-9 rhombic leaf lobes, its appressed, flakey stipules, and its inflorescences, which bear many more fruits that are each smaller and more globose. One of the syntypes (R. Kanehira 2452) cited in the protologue of Boerlagiodendron pachyphyllum belongs to this new species. We are happy to name this species after the Palau resident and naturalist, Ron Leidich, whose generosity enabled the discovery of this species and for his inspirational knowledge and enthusiasm about Palau’s natural history.

Specimens examined.

Palau. Koror State: Ngeremdiu Beach, 6 Jun 2014 (ster.), C. Costion 3708 (US); Ngeremdiu Beach, 6 Jun 2014 (fl.), C. Costion 3709 (BNM); Ngeremdiu Beach, 6 Jun 2014 (fl.), C. Costion 3710 (NY, US); Ngeruktabel Island, 26 Jun 1982 (fr.) Hobdy 1547 (BISH); uninhabited coral island, 14 Aug 1933 (ster.) R. Kanehira 2452 (TI, FU); Ngeruktabel Island, 8 Aug 2007 (fr.) M. Balick 4511 (BNM, NY); Ngeruktabel Island, along path from boat landing to German Lighthouse, 07°15'50.3"N; 134°26'45.9"E, 135 m, 9 Nov 2013 (ster.), G.M. Plunkett 2707 (BNM).

Figures

Figure 1. Osmoxylon leidechii a compound inflorescence with flowers b compound inflorescence with fruits c fertile flowers and sterile fruits d individual inflorescences with fruits e petiolar stipule side view and stipule crests f petiolar stipule overhead view g leaf.