Boehmeria multiflora

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 : 139-141

19. Boehmeria multiflora C.B.Rob. — Fig. 17 ; Map 19

Boehmeria multiflora C.B.Rob. (1908) 179. ― Type: R.S. Williams 1088 (iso NY), Philippines, Luzon , Benguet, Baguio, 6 June 1904 .

Shrub or small tree, 2–5 m tall; ultimate branches 1–2 mm diam, indumentum dense, velvety, hairs short (c. 0.3–0.4 mm long), robust, ± spreading, white. Stipules linear-ovate, long-acuminate, 8–13 by 2–2.5 mm, thick-textured, hairy, hairs on midrib dense, ± adpressed, longer than on stem, elsewhere sparse very short and fine. Leaves opposite, not or moderately dimorphic with ‘larger’ leaves 1.2–2 × length of ‘smaller’ ones and relatively narrower with more distinctly acuminate apex; slightly asymmetrical, narrowly ovate, small to medium-sized, 9–14 by 3–5 cm, relative proportions little-varying, length 3(–4) × width; margin finely serrulate, teeth (30–)35–45(–55) either side, up-curved, blunt, c. 1 by (1–)1.5–2(–4) mm; leaf apex long-acute to long-attenuate and often slightly sideways-curved; base asymmetrically rounded or slightly cuneate; basal veins extending just into distal half of lamina, upper lateral veins 3–4 but often indistinguishable from coarser tertiary veins, usually all arising in distal half of lamina, these and fine reticulation robust and prominent abaxially; texture fairly thick-chartaceous and leaves usually slightly bullate; adaxial surface with abundant hairs like the stem but softer, pale or brownish; hairs on abaxial surface denser, greyish; petiole very variable relative to lamina, (0.1–)0.2–0.3 × length, 1–4 cm long. Flower­clusters borne along leafless inflorescence-bearing axes, these unbranched (or rarely male branched), pendulous or apically drooping, 1 per axil, plants mostly bisexual, with male axes up to 11 cm long borne in upper axils, female axes 15– 30 cm long borne in lower leaf axils, some intermediate axes with bisexual clusters; bracts c. 1.5 mm long, narrowly triangular long-acuminate; flower-clusters closely-spaced or (especially female) contiguous along axis, male clusters c. 3 mm diam with less than 10 loosely arranged flowers, female clusters 5 – 6 mm diam, with 30–more than 50 densely crowded flowers; bracteoles in male clusters narrowly triangular or obovate up to 0.4 mm long, in female clusters narrower, linear-ovate, up to 0.7 mm long, c. half length of fruiting perianth. Male flowers 4-merous, sessile, mature buds depressed-globose, c. 1.5 mm diam, tepals with apiculus and without dorsal appendages or sometimes with distinct dorsal thickening, with dense indumentum like the stem. Female flowers ovoid to obovoid, up to 0.7 by 3 mm, beaked; stigma small, 0.8–1 mm long, hooked. Fruiting perianth obovoid to spindle-shaped (tapering to base and to distinct apical beak), up to 1.5 by 0.7 mm, much-flattened with indistinct or distinct marginal wing, hairs sparse or abundant, short, fine, spreading. Achene ellipsoid, c. 0.6 mm long.

Distribution ― Philippines (Luzon, Bohol, Mindanao), Indonesia (Bouton [also Buton or Butung, island adjacent to Sulawesi]).

Habitat & Ecology ― Margins of pine and oak or oak-ericaceous forest; disturbed roadsides in forest; 750–2600 m altitude.

Conservation status ― Vulnerable (VU). The species is known from c. 30 collections, most of them more than 50 years old. Its main distribution is on Luzon in the Philippines; as discussed under B. beyeri and B. heterophylla , the Philippines are subject to severe and continuing habitat degradation. The EOO of 601 968 km 2 is misleading because of the many old records and the single (old) record that documents the extension to Sulawesi, the AOO is calculated as less than 500 km 2 and it is recorded from only c. 30 collections. For these reasons we will propose the criterion VU B2ab(iii).

Notes ― 1. This species is distinctive in leaves relatively narrow, with spreading indumentum on both sides (velvety abaxially), often slightly bullate with prominent reticulation. It is similar in general appearance to two other narrow-leaved taxa, the partly sympatric but more widespread B. densiflora var. densiflora which differs in leaves mostly narrower (length 4–10 × width, rather than 3(–4) × width) with adpressed hairs adaxially and marginal teeth shallow, acute, mostly more widely spaced, and the allopatric (Indian subcontinent to China and Indochina) B. penduliflora which differs in much narrower glabrescent leaves with more than 50 acute teeth.

2. Boehmeria multiflora can be confused with certain densely-pubescent forms of B. virgata var. virgata which differ in inflorescence-bearing axes usually branched and generally longer (male 10–20 cm rather than ≤ 10 cm, female up to 70 rather than ≤ 30 cm), leaves not bullate, often longer and relatively broader, marginal teeth relatively broader, upper veins only 1–2(–3), basal veins reaching nearly to tip. However, these densely hairy forms of B. virgata are found mostly in the island of New Guinea whereas its forms found in the Philippines are mostly much more easily distinguished, being sparsely adpressed-hairy and broader-leaved.

3. Boehmeria multiflora can also be confused with narrower-leaved forms of the sympatric B. rugosissima which differs in leaves relatively broader with length at most 2.5 × width, only sparsely hairy adaxially, and inflorescence-bearing axes branched.

4. Boehmeria multiflora is possibly under-collected and might be expected to occur also in the intermediate islands of the Central Philippines.

Figures

Map 19 Distribution of Boehmeria multiflora C.B.Rob.

Fig. 17 Boehmeria multiflora C.B.Rob. a. Habit of stem with inflorescence-bearing axes; b. leaf; c. leaf, detail of adaxial surface; d. detail of leaf margin and abaxial surface; e. stipule; f. detail of male inflorescence-bearing axis showing one flower-cluster (inflorescence) and bract; g. detail of female inflorescencebearing axis showing one flower-cluster (inflorescence); h, i. fruiting perianths of different form (from different plants) (a, i: Elmer 21976, K; b–e, h: Gaerlan 26686, L; f: Elmer 14275, K; g: Williams 1088, K). — Scale bars: a = 2 cm; b = 1 cm; c, d, f-i = 1 mm; e = 2 mm.