Polyosma pachyrhachis Schulze-Menz ex B.J.Conn & O.K.Paul, 2024

Paul, O. K., Conn, B. J. & Henwood, M. J., 2024, Taxonomic review of Polyosma (Escalloniaceae) in Papuasia, Blumea 69, pp. 54-88 : 81-82

25. Polyosma pachyrhachis Schulze-Menz ex B.J.Conn & O.K.Paul , sp. nov. — Fig. 13

Etymology. The specific epithet ( pachyrhachis ) refers to the thick, stout

(pachy -) axis of the inflorescence axis (- rhachis) characteristic of this species. Polyosma pachyrhachis is morphologically most similar to P. ilicifolia , but differs by having slightly larger obovate,sometimes elliptic leaves (13.5–16 by 5–7 cm vs oblong to narrowly elliptic leaves 9–11 by 3–4 cm for P. ilicifolia ), and the mature corolla remains tubular at anthesis, with 4 small ovate lobes in P. pachyrhachis (vs P. ilicifolia has mature corolla fully split into 4 petals). — Type: L.J. Brass 32162 (holo LAE [ LAE 33906]; iso L [L 0035110]), Papua New Guinea, Eastern Highlands, Mt Elandora, 18 Oct. 1959.

Tree, c. 6 m tall. Branchlets hairy, pustules grey, scattered. Leaves sparsely hairy; petiole 2–2.5 cm long; lamina obovate, sometimes elliptic, 13.5–16 by 5–7 cm, coriaceous, upper surface drying brown, glaucous on abaxial surface; base acute, margin serrate, apex acuminate; secondary veins 20–28 on each side and at an angle greater than 45° from midrib, regularly looping near margin onto the next secondary vein; tertiary veins weakly percurrent, pubescent, prominent on abaxial surface. Inflorescence racemose, terminal, 20–30-flowered; rachis 5–19 cm long, densely hairy; flowers clustered along rachis; pedicels c. 3 mm long, thick; bracteoles 2–3 mm long, hairy. Calyx lobes 3–5 mm long. Corolla buds tubular, 10–20(–30) mm long, green with yellowish tinge, rarely yellow; corolla moderately hairy, remaining tubular at anthesis, except opening with 4 small lobes distally. Fruits not seen.

Distribution — Indonesia (Papua Barat) and Papua New Guinea (Western Highlands, Eastern Highlands, Southern Highlands).

Habitat & Ecology — Occurring in montane forest at elevations of about 2 400 m.

Conservation status — Unknown.

Additional specimens examined (Paratypes). INDONESIA, Papua Barat, Vogelkop,Anggi Gita Lake, H.O. Sleumer & W. Vink BW 14051 & BW 14115 (L). – PAPUA NEW GUINEA, Western Highlands,Ambun, J.R. Flenley ANU 266 ( LAE ); Sirunke, J.S. Womersley NGF 14275 (L); Southern Highlands, Mt Giluwe, J.R. Croft LAE 60628 (L, LAE ); J.R. Croft LAE 60920 ( LAE, NSW ); Kiburu, R. Schodde 14437 ( LAE ).

Notes — 1. Other morphological differences between P. pachyrhachis and P. ilicifolia include: P. pachyrhachis has bracteoles (2–3 mm long), calyx lobes (3–5 mm long) and corolla (10–20 mm long) that tend to be longer than in P. ilicifolia (vs bracteoles c. 2 mm long, calyx lobes c. 2 mm long, and corolla c. 10 mm long).

2. Polyosma pachyrhachis is also morphologically similar to a few other species, namely P. induta , P. longebracteolata , and P. schulzemenzii , but differs from them by having leaves with an acuminate apex (vs apex obtuse to subacute in P. longebracteolata and attenuate in the other two species); and it differs from P. longebracteolata by having larger leaves (13.5–16 cm long, 5–7 cm wide, vs 0.2–0.5 cm long, 0.5–1.8 cm wide in P. longebracteolata ). Furthermore, the bracteoles of P. pachyrhachis are shorter than the calyx, whereas they are as long as the calyx in P. longebracteolata .

Figures

Fig. 13 Isotype collection of Polyosma pachyrhachis Schulze-Menz ex B.J.Conn & O.K.Paul (L.J. Brass 32162 [L 0035110]).