Boehmeria subintegra Friis & Wilmot-Dear

Wilmot-Dear, C. M. & Friis, I., 2013, The Old World species of Boehmeria (Urticaceae, tribus Boehmerieae). A taxonomic revision, Blumea 58 (2), pp. 85-216 : 145-147

22. Boehmeria subintegra Friis & Wilmot-Dear — Fig. 20 ; Map 22

Boehmeria subintegra Friis & Wilmot-Dear in Wilmot-Dear et al. (2010) 444. ― Type: Brass 23704 (holo K;iso A), Papua New Guinea, Milne Bay,Gwariu River, Biniguni camp, 30 July 1953.

Shrub or small tree, 2–4 m tall, with erect branches; ultimate stems slender (but soon becoming thick and woody), c. 1 mm diam, hairs dense, short fine, closely-adpressed, white; later glabrescent. Stipules narrowly triangular-attenuate, ± free to base, fairly long and conspicuous, 7–8 by c. 1 mm, but very soon caducous. Leaves opposite, dimorphic in size and shape, usually markedly so, with ‘larger’ leaves, (1.5–)2–4 × length of ‘smaller’ ones and relatively narrower, slightly sideways-curved, linear-ovate to narrowly elliptic-ovate, fairly small, (3.5–)5–12 by (1–) 1.5–3 cm, length 3.5–4 × width; margin often ± entire and slightly undulate throughout most of its length but towards leaf apex indistinctly serrate, teeth 10–12(–15) either side, indistinct shallow, sometimes up to 0.2 mm long but often reduced to slight thickening or tiny mucro, very widely spaced, 2 – 5 mm apart; leaf apex gradually attenuate to ± long-acuminate, sometimes mucronate at extreme tip; base narrowly cuneate; basal veins extending into distal third or nearly to tip, upper lateral veins similarly arranged on both sides of leaf, 2–4 either side but scarcely distinct from coarser tertiary veins, lowermost arising just in distal half of lamina; inconspicuous (rarely impressed) adaxially, finely prominulous abaxially; texture fairly thin-chartaceous to (dry habitat) very thin-coriaceous, adaxial surface glabrous and shiny (dark green when live); abaxial surface paler, hairy on veins, hairs sparse or dense, adpressed; petiole short relative to lamina, 0.1–0.25 × lamina length. ‘Smaller’ leaves relatively broader, broadly elliptic or ovate with apex obtuse, broadly acute or rarely short-acuminate, extreme tip usually also distinctly mucronate, mucro 1– 2 mm long, base broadly cuneate. Flower­clusters borne on leafless inflorescence-bearing axes, these pendent, unbranched, unisexual, 1 per axil, male axes up to 10 cm long, female ones very variable in length, 10–35 cm long; bracts narrowly triangular, c. 2 by 0.5 mm, soon caducous; flower-clusters spaced 2–5 mm apart, male clusters up to 2 mm diam, with 1–5 flowers, female clusters c. 2.5 mm diam, with 10–30 flowers; bracteoles inconspicuous, linear-elliptic, 0.3–0.5 mm long. Male flowers 4-merous, pedicels 0.5–1 mm long, mature buds c. 1 mm diam, dorsal appendages of tepals small, hairs sparse coarse stiff ± spreading hairs. Female flowers c. 0.6 by 0.3 mm, ellipsoid, hairy like male; stigma 1–1.5(–2) mm long. Fruiting perianth obovate in outline and extremely laterally flattened, with distinct marginal wing surrounding the part filled by the achene, 1–1.5 by c. 0.8 mm. Achene located in middle or distal part of fruiting perianth.

Distribution ― Papua New Guinea.

Habitat & Ecology ― Ridge forest, secondary forest, brushy seral growth on ravines and steep riverbanks, regrowth vegetation on steep slope, grassy slopes ( Arundinella ); 200–1760 m altitude.

Conservation status ― Vulnerable (VU). The conservation status was established by Wilmot-Dear et al. (2010: 448). The species is known from five localities and 11 collections, mainly made between 1935 and 1953 in remote areas of Papua New Guinea, and the EOO is 16 604 km 2, while the AOO is 16 km 2, according to which it is endangered. However, the remoteness of the region in which the species occurs would seem to indicate that it is not currently threatened.

Notes ― 1. An endemic of restricted distribution and one of only four species known from the island of New Guinea, the others being B. virgata (three varieties), B. depauperata and B. heterophylla , none of which would be confused with it. It is very distinctive in the whole genus in its relatively small leaves which are so indistinctly toothed as to appear almost entire, and in its ‘smaller’ leaves usually conspicuously long-mucronate. The Burmese endemic B. kurzii is the only other Old World species with entire (but truly entire) leaves and is otherwise very dissimilar.

2. The long pendulous unbranched crowded inflorescence-bearing axes with broadly-winged fruiting perianths are like those of B. penduliflora , B. multiflora and B. densiflora (this last also has well-spaced teeth and somewhat similar leaf shape), but leaves in all three are easily distinguished by being uniformly and distinctly toothed throughout.

Figures

Map 22 Distribution of Boehmeria subintegra Friis & Wilmot-Dear (Ê), B. virgata (G.Forst.) Guillem.subsp. virgata var. velutina Friis & Wilmot-Dear (●), B. virgata (G.Forst.) Guillem. subsp. virgata var.maxima Friis & Wilmot-Dear (ä) and B. virgata (G.Forst.) Guillem.subsp.virgata var.austroqueenslandica (Domin) Friis & Wilmot-Dear ().

Fig. 20 Boehmeria subintegra Friis & Wilmot-Dear. a. Habit of stem with inflorescence-bearing axes; b. leaf; c, d. detail of leaf margin and abaxial surface (different plants); e. pair of stipules; f. detail of male inflorescence-bearing axis with flower-cluster (inflorescence) and bract; g. male bud; h. detail of female inflorescence-bearing axis with flower-cluster (inflorescence); i. fruiting perianth (a, e, i: Brass 23704; b, c, f, g: Hoogland 3988; d: Stevens 58169; h: Carr 15315; all K). — Scale bars: a = 2 cm; b = 1 cm; c–e = 2 mm; f–i = 1 mm.