Zygogynum montanum (Lauterb.) Vink

Vink, W., 2016, The Winteraceae of the Old World. VIII. Some Zygogynum species from New Guinea, Blumea 61 (1), pp. 41-50 : 47-48

10. Zygogynum montanum (Lauterb.) Vink — Fig. 1

Zygogynum montanum (Lauterb.) Vink (1985) 53. — Tetrathalamus montanus Lauterb. (1905) 319; (1923) 15; B. L . Burtt (1938) 458. — Bubbia montana (Lauterb.) A.C.Sm. (1942) 426. — Type: Schlechter 13984 (holo B †; iso BO, K) .

Shrub 2 m high. Branchlets slender, dark brown, sometimes with myrmecodome. Leaves scattered; petiole 8– 25 mm long, groov- ed to flat above, rounded below, dark brown; blade narrowly obovate, 7–27 by 2.5–8.5 cm, chartaceous, greenish grey to light brown below; apex acute and 0–27 mm (broadly) acuminate, base (narrowly) acute (to slightly attenuate); midrib impressed above, prominent below; secondary nerves at 55–70° with midrib, arcingly joined at some distance from midrib, prominulous on either side. On lower leaf surface stomata white, dense, solitary and in clusters, also over secondary nerves; oil cells in young leaves very distinct, in mature leaves less distinct to obscure. Inflorescences with 3–5 partial inflorescences, these 3–11 cm long, with very slender axes, 7–50-flowered, flowers inserted on axes (1st or) 2nd to 3rd (to 4th) order; empty bracts below inflorescence 0–3; pedicels 2–10 mm long, very slender, with minutely convex cells and oil cells. Calyx 2–3- or irregularly lobed. Petals 4 – 8, free, obovate to oblong, green or greenish white, outer ones 4–6 by 2–4 mm, inner ones 3.5–4 by 1.5–1.8 mm, apex rounded. Stamens 10–17, 1 mm long; thecae apically touching; pollen in tetrads. Carpels 2 –5, free to coherent, 1.3–1.5 by 1–1.3 by 1–1.3 mm; stigma 0.3–0.6 as long as carpel apex, not descending adaxially; ovules 3–6. Fruitlets a soft berry, globose, red, in sicco flattened and in centre showing seeds, 15 mm diam; apparently without stipe; fruitwall without brachysclereids; pulpa not between seeds. Seeds several, obovoid with shortly narrowed base, 7–7.5 by 4.5–5 by 4–4.5 mm; testa hard, dull black, smooth.

Distribution — PNG, Bismarck Mts to Mt Dayman.

Ecology — Undergrowth in (Lithocarpus­Castanopsis­Anisoptera) forest at 240–1200 m altitude. Flowering January–July, fruiting July.

Specimens examined. PAPUA NEW GUINEA, Gulf Prov., above Purari R., 63 km NE from Baimuru, Croft LAE 61131 (L), 240 m alt.; Madang Prov., Bismarck Ra., Schlechter 13984 (B†, BO, K), 1200 m alt.; Morobe Prov., Gurakor, Brass 29487 (A, CANB,L, US), 640 m alt;Milne Bay Prov., Maneau Ra., N slopes of Mt Dayman, Brass 23545 (A, LAE ), 700 m alt.

Notes — This species is distinct by its thin leaves, delicate flowers and a soft berry with relatively large smooth seeds; the low number of ovules is notable.

Z ygogynum longifolium from Papua is very similar (often also with myrmecodomes), but its leaves are purplish grey below, its stigma is as long as the carpel apex, and the seeds are rough or with ribs or flanges.

Z ygogynum oligocarpum has also a longer stigma; the apex of its leaves is more rounded.

The Z. montanum collection from the Bismarck Ra. has 7 or 8 petals in two series, the other collections have 4– 6 petals in one (4 petals) or two (2 by 3 petals) series.

Figures

Fig. 1 Carpels, all with ventral side to the left, and at the same magnification. – a. Zygogynum archboldianum; b. Z. bosavicum; c. Z. clemensiae; d. Z. cruminatum; e. Z. cyclopensis; f. Z. ledermannii; g, g'. Z. longifolium; j. Z. megacarpum; h. Z. montanum; i. Z. oligocarpum; k, k'. Z. polyneurum; l. Z. schramii; m. Z. sororium; n. Z. staufferianum; o. Z. umbellatum (a. Brass 12712; b. LAE 58822; c. Clemens 4596; d. LAE 69143; e. Royen & Sleumer 6396; f. Takeuchi 6212; g. Vink BW 8413; g'. Robbins 2004; j. Burley & Ismail 4618; h. LAE 61131; i. Schlechter 16470; k, k'. Jacobs 9489; l. Vink BW 8458; m. Ledermann 11898; n. Balgooy 968; o. Boden Kloss s.n.).