Osmoxylon pachyphyllum (Kaneh.) Fosberg & Sachet, 1980

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 : 54-57

Osmoxylon pachyphyllum (Kaneh.) Fosberg & Sachet Fig. 4

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

Type.

Palau. Aimeliik: 1933 (fr.), R. Kanehira 2301 (lectotype: FU!, here designated; isolectotype: TI!).

Description.

Small to medium sized understory, tree 7-15 m tall, sparsely branched. Leaves palmately lobed, variable in size, up to 60 cm long and 65 cm wide (generally smaller), with 5-7 lobes; margins sparsely dentate with serrations exserted from margin, 1 per prominent secondary vein or alternating between veins; prominent secondary veins meeting the mid-rib (near) perpendicular then curving to a 30-45°an gle; petiolar crests 1-2, rarely 3, firm with sharp edges, sparsely ciliate; stipules not appressed to stem, strongly recurved, glabrous, tip sharp to the touch. Inflorescence 7-15 cm in diameter, primary axis bearing 12-15 secondary inflorescence units, secondary axis (from primary axis to where lateral umbellules are attached) c. 2.8 cm long, with c. 30 pinkish-red baccate pseudo-fruits, c. 4 mm in diameter; peduncles jointed, c. 2.6 cm long, top segment shorter, maturing to equal the length of the bottom segment, green. Fertile flowers 10-15, with greenish-yellow, fused calyx crowning the ovary; corolla tube yellowish-orange, 6 lobed, c. 5 mm long; stamens alternate to the petal lobes, strongly exserted; ovary inferior, stigmas sessile. Fruits flat sided, 1.2-1.5 cm long, 0.7-0.8 cm wide, greenish with reddish-dull purple apex and striations down to the base, c. 3-5 per umbellule; fertile fruiting umbellules loosely organized with distinct peduncles, 1.5-3 cm diameter.

Notes.

As circumscribed herein, Osmoxylon pachyphyllum is known only from volcanic soils on Babeldaob Island. Previous collections of this species from the limestone islands (including a syntype, R. Kanehira 2452) are now referred to the new species Osmoxylon leidichii . In addition to its geography and ecology, Osmoxylon pachyphyllum can easily be distinguished by its 5-7 lobed and weakly serrated leaves, its oblong, large, angled fruits, and its umbellules, which have very few (3-5) fruits, compared to all other species known from Palau. The stipule at the petiole base is also distinctive among the Palauan members of the genus in being strongly recurved, pointing away from the stem, and with a noticeably sharp tip.

Specimens examined.

Palau. Aimeliik State: slope of Ngetchum, 28 Dec 2005 (fl.) C. Costion 894 (BNM); Jul 1933, Kanehira 2301 (FU); 30 Jul 1933, Kanehira 2311 (FU); Babeldaob Island, south central Babeldaob, SW of Mt. Yekigoroto, 2 Sep 1965 (fr.), R. Fosberg 47677 (BISH); Babeldaob Island, 17 Apr 1938 (flw), Hatusima 5021 (FU); Babeldaob Island, 18 April 1938, Hatusima 5053 (FU); Melekeok State: Ngardok Nature Reserve in Ngardok forest dynamics plot, Jul 2014 (fr.,fl.) C. Costion 3779, 3780, 3781, 3802 (BNM, US); Ngardmau State: 2005 (fr.), C. Costion 90 (BNM); Ngertebechel watershed south of waterfall, 15 Jul 2005 (fl.), C. Costion 449 (BNM); Ngaremlengui State: along trail from Mr. Ha’s quarry to Parkia population and waterfall, 07°32'39.6"N; 134°34'07.2"E, 131 m, 5 Nov 2013 (bud, fl., fr.), G.M. Plunkett 2686 (BNM, NY); Ngechesar State: along Iliud ra mesiual historic trail, 99 m, 7 Jun 2014 (fr.) C. Costion 3712 (BNM, US), 7 Jun 2014 (fr.) C. Costion 3713 (NY), 7 Jun 2014 (fl.) C. Costion 3714 (NY), 7 Jun 2014 (fr.) C. Costion 3715 (BNM, NY, US), 7 Jun 2014 (fl.) C. Costion 3716 (BNM, US), 7 Jun 2014 (fl.) C. Costion 3717 (US), 7 Jun 2014 (fr.) C. Costion 3719 (NY, US)

Figures

Figure 4. Osmoxylong pachyphyllum a compound inflorescence with mature flowers b compound inflorescence with immature flowers c compound inflorescence with mature fruits d two inflorescences with mature fruits e mature leaf f petiolar stipule and petiole crests.