Boehmeria lanceolata Ridl.

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 : 123-125

11. Boehmeria lanceolata Ridl. — Fig. 10a–j ; Map 13

Boehmeria lanceolata Ridl. (1911, nec 1910) 94. ― Type: Ridley 14645 (holo K; iso BM), Malaysia, Perak State, Tenmangoh , July 1909.

Boehmeria tonkinensis Gagnep. (1928) 127. ― Syntypes: Petelot 723 (P), Vietnam, Tonkin, Pia-ouac; Poilane 10474 (P; isosyn A), Vietnam,Annam, Mai Lanh , pres de Quang Tri, 21 May 1924; Poilane 12172 (P), Laos, Tchepone ; McClure 9146 (P), China, Hainan. – See Note 1.

Boehmeria lohuiensis S.S.Chien in Chun et al. (1963) 355,syn.nov. ― Type: Z.S. Chung 534 (holo HC), China, Hainan, Lohui Dist. , 15 Sept. 1953. – See Note 2.

Shrub or subshrub, 1–2 m tall; ultimate branches quadrangular, up to 1.2 mm diam, hairy, hairs abundant but inconspicuous, adpressed. Stipules linear, fairly long, c. 9 by 1.2 mm, glabrous very soon caducous. Leaves opposite, not or slightly dimorphic in size with ‘larger’ up to 1.5 × length of ‘smaller’ and sometimes relatively narrower, ± symmetrical, linear-oblong-obovate (i.e., margins almost parallel for most of length, but widest above the middle), small or medium-sized, 6–11(–14) by 3(–5.5) cm, length 3.5–more than 4 × width; margin dentate with 20–30 teeth (number increasing with leaf-size), 0.5–1 by 3 mm, rather rounded in outline but each with an abruptly apiculate tip; leaf apex broad-acute or with short indistinct broad acumen; base gradually attenuate to short-cuneate or narrowly rounded, outline of base and apex often similar; basal veins extending into distal third or nearly to tip, upper lateral veins 1–2(–3) either side but very indistinct, with lowermost arising in distal quarter or third, inconspicuous adaxially, basal veins finely prominent abaxially; coarser tertiary venation somewhat scalariform often visible abaxially; texture thin-chartaceous; glabrous adaxially (or with occasional single hair in centre of areoles, these always present in very young leaves at stem apex), adaxial surface with numerous cystoliths; abaxial surface hairy on veins only, hairs very sparse, inconspicuous, adpressed; petiole 0.5–2.5 cm long, only 0.1–0.2 × lamina length. Flower­clusters borne on leafless axes, these straight erect, up to 11 cm long, 1 per axil, but often with 1– 2 branches close to base and thus appearing as if several axes from axil; clusters spaced only 1–3 mm apart and thus almost contiguous when mature, 2 –3 mm diam, male clusters in distal part of axis with up to 10 flowers, female clusters proximal with up to c. 15 flowers; bracteoles broadly triangular but minute, inconspicuous, <0.3 mm long. Male flowers 4-merous, sessile or subsessile, mature buds c. 1 mm diam, tepals with very distinct dorsal appendages up to 0.2 mm long, sparsely hairy. Female flowers with stigma only 0.8–1.2 mm long. Fruiting perianth very short and broad, 0.8– 0.9 by 0.7 mm, subspherical-obovoid (to ovoid) with broadly rounded base, variable either scarcely laterally flattened and with no marginal rim or distinctly laterally flattened with marginal wing-like rim to 3–4-angled; glabrous or short-spreading-hairy. Achene filling fruiting perianth.

Distribution ― Southern China (including Hainan), northern Vietnam, Laos, Thailand, Malaysia (Perak).

Habitat & Ecology ― Primary season or mixed evergreen and deciduous forest, secondary forest, thickets, moist open areas, rocky areas in ravines; 180–700 m altitude.

Conservation status ― Near Threatened (NT). The species is known from only 20 collections, some of which are recent, from fairly scattered locations, with some considerable gaps in the range. The EOO of 1 153 440 km 2 is therefore probably exaggerated. The AOO gives a figure of less than 500 km 2. It occurs in a moderate range of habitats, mainly forests, and although the habitats are not currently threatened by serious degradation, and it therefore does not meet the criteria for a formal status of Vulnerable (VU), it may become so in the future with increasing agriculture in the region.

Notes ― 1. Boehmeria tonkinensis was reduced to synonymy by Chen et al. (2003, 2005), since its distinctive characters fall within the range of variation of B. lanceolata (Ridley was mistaken in describing the male flowers of B. lanceolata as 5-merous). Hainan and Tonkin have a very similar flora with many species in common, these often localised around the Beibu [ Tonkin] Gulf.

2. Boehmeria lohuiensis is here reduced to synonymy. Although the type has not been seen, its identity is clear from its description and diagnosis. The leaves are larger than otherwise seen (up to 14 cm rather than 11 cm long) and marginal teeth are stated to be ‘larger’ (size not stated) but other stated differences (leaf base cuneate, inflorescence-bearing axis up to 10 cm long, branched dichotomously at base and with scattered clusters) in fact fall within the range of variation of B. lanceolata . In addition, many of the particularly distinctive features of B. lanceolata (leaves thin-textured ± glabrous, marginal teeth sharply apiculate, flowers minute and fruiting perianth very small ovoid), are clearly depicted in the ample description.

3. Boehmeria lanceolata is apparently rare (only a few populations so far known), but probably also under-collected, only one collection so far seen from each of Laos, Thailand and Malaysia. It is easily distinguished from all other species of Boehmeria by its leaves linear-oblong-obovate (i.e., margins almost parallel for most of length, but widest above the middle) with base and apex similar in outline or with base more tapering than apex and its fruiting perianth small almost spherical with a broadly rounded base.

4. It can also be distinguished from most taxa by its leaves being thin-textured, ± glabrous adaxially, with long basal veins and few upper veins, and its inflorescence-bearing axes short, slender, erect, dichotomously branched close to base. The partly sympatric B. hamiltoniana is somewhat similar but leaves are membranous often relatively narrower, stems glabrescent and female inflorescence-bearing axes ± pendulous, often longer. The partly sympatric B. densiflora is also similar in general appearance, but has inflorescence-bearing axes unbranched, solitary and leaves often thicker-textured.

Figures

Map 13 Distribution of Boehmeria hammiltoniana Wedd. (▲) and B. lanceolata Ridl. (●).

Fig. 10 a–j: Boehmeria lanceolata Ridl. a. Habit, upper part of stem with inflorescence-bearing axes; b. leaf; c. detail of leaf apex; d. stipule; e. detail of male inflorescence-bearing axis showing one cluster (inflorescence); f. detail of female inflorescence-bearing axis showing one cluster (inflorescence); g–j. fruit- ing perianths of different form (from same plant: g, h. unribbed; i. four-angled; j. fruiting perianth with marginal rim). — k–n: Boehmeria hamiltoniana Wedd. k. Leaf; l. detail of leaf margin; m. detail of male inflorescence-bearing axis showing one cluster (inflorescence); n. fruiting perianth (a–f: Hiep 130; g–j: Tsang 30455; k, l: Gamble 7291; m, n: Clarke 27246; all K). — Scale bars: a, b, k = 2 cm; c, e-j, m, n = 1 mm; d, l = 2 mm.