Boehmeria pilosiuscula (Blume) Hassk.

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 : 199-201

32. Boehmeria pilosiuscula (Blume) Hassk. — Fig. 38 ; Map 40 , 41

Boehmeria pilosiuscula (Blume) Hassk. (1844) 79. ― Urtica pilosiuscula Blume (1825) 491. ― Boehmeria platyphylla D.Don var. pilosiuscula (Blume) Hand.-Mazz.(1929) 151. ― Type: Kollmann s.n. (holo G; iso NY), Indonesia, Jawa [Java], “montosis”. – See Note 1.

Woody-based herb or subshrub, erect, up to 1.5 m tall, or decumbent, trailing or scrambling and often rooting at nodes, stems 0.3–5 m long; ultimate stems slender, c. 0.8 mm diam, with soft spreading hairs of two kinds,dense minute (<0.1 mm) and straight mixed with sparse long (0.2–0.4 mm) and curved. Stipules triangular and often small, 4–7(–10) by 1–1.5(–2) mm, chartaceous. Leaves opposite, moderately dimorphic with ‘larger’ 1.3–2 × length of ‘smaller’ ones and relatively narrower, broadly elliptic to elliptic-ovate or elliptic-obovate, lamina varying in shape often even on one plant, some leaves almost symmetrical, others distinctly asymmetrical with two sides of lamina of similar width but different outlines; small or medium, 3–12(–15) by 1.5–6(–8) cm, length (1.7–)1.8–2(–2.25) × width; margin serrate, teeth 25–40(–45) either side, 1–2 by 2–3(–4) mm, broader rather than more numerous in larger leaves and usually slightly up-curved; leaf apex with abrupt short or relatively long acumen toothed to tip, base distinctly oblique with one side rounded, the other side cuneate; basal veins rather straight, fine but distinct, extending into distal third, upper lateral veins similarly arranged on both sides of lamina, 1– 2 arising near middle of lamina or in distal half but not very distinct from reticulation which is also visible adaxially and finely prominent abaxially; texture usually rather thin-chartaceous, but leaves often slightly bullate; hairs on adaxial surface all of same kind, sparse or abundant, adpressed or ± spreading, on abaxial surface those on veins fairly long (0.2–0.7 mm) spreading, sparse or abundant, elsewhere minute, inconspicuous and sparse; petiole relatively long relative to lamina, often just over half of lamina length, up to 4 cm, with two kinds of hairs like the stem. Flower­clusters borne on leafless inflorescence-bearing axes, 1 per axil; erect and short; bisexual or unisexual; entirely or predominantly male axes rarely seen, 4–6 cm long, with several shorter lateral branches in lower half which are up to 2 cm and progressively shorter towards axis apex, with female clusters (where present) restricted to a few along main axis; entirely female or predominantly female axes much more common, unbranched, only 1–6(–10) cm long with groups of female clusters so closely contiguous and densely congested that the axis appears to be ± cylindrical, a dense mass of tightly congested flowers, sometimes with well-marked sterile basal portion or gaps between groups of clusters; if bisexual then also with a few small few-flowered male clusters near tip of axis only, these congested or spaced 2–3 mm apart; male clusters 1.5–2(–3) mm diam, with few–10 flowers, female clusters large, (3–) 4–7 mm diam, with (30–)usually well over 50 densely crowded flowers; bracts subtending male clusters abruptly fine-acuminate, c. 1–2 mm long, bracts subtending female clusters inconspicuous; bracteoles narrowly oblong, fairly conspicuous (in crowded female clusters only when fruit fallen), 0.5 mm long. Male flowers 4-merous, on pedicels 0.5–1.5 mm long, mature buds globose, c. 1.5 mm diam, dorsal appendage of tepals distinct, hairs of two kinds, sparse, short, adpressed and longer hooked. Female flowers 0.7–0.8 by 0.2–0.5 mm, narrowly obconical to broadly obovoid-truncate, often with abrupt beak to half of perianth length or often conspicuously 2-toothed, hairs abundant, spreading, long, white, hooked; stigma c. 1 mm long. Fruiting perianth 1–1.2 by 0.8–1 mm, broadly obconical-flattened (i.e., obtriangular in outline) with or without minute abrupt beak, dorsiventrally flattened near apex forming winged ‘shoulders’ in distal half, abundantly hairy in distal part. Achene rather asymmetrically ellipsoid or obconical– 3-angled, relatively flattened, shiny yellow-brown almost as long as fruiting perianth, ± rugose.

Distribution ― India (Tamil Nadu, Arunachal Pradesh), Sri Lanka, Burma, southern China (incl. Hainan and Taiwan), Thailand, Indonesia (Sumatera, Jawa, Borneo, Nusa Tenggara [Lesser Sunda Islands]), Philippines (Luzon).

Habitat & Ecology ― Moist areas in evergreen forest, often by streams; or in clearings in disturbed areas or on roadside banks; sea level– 1650 m altitude.

Conservation status ― Near Threatened (NT) or possibly Vulnerable (VU). The species is known from c. 150 collections, some of which are recent, but appears to occur in only c. 25 rather scattered locations in India, Indochina, Indonesia and the Philippines. Thus the EOO of over 8 000 000 km 2 is extremely misleading. Its AOO is less than 500 km 2 and it occurs in fairly restricted forest habitat. The record from southern India may well represent a population now extinct as the region is extensively cultivated, and habitats in Taiwan, the Philippines and Jawa are increasingly degraded; those in China and Indochina are not currently so but may become so in the future with increasing agriculture. Those in the mountain ridge in West Sumatera are not currently threatened. Tentatively it is given the status of Vulnerable (VU) on the criteria VU B2ab(iii).

Separate formal assessments are not given for the two, intergrading, varieties.

Notes ― 1. The collector of the type of B. pilosiuscula, Kollmann , is not cited in Blume’s protologue but the label on the specimen in G has the basionym written in Blume’s handwriting, which strongly indicates this collection is the holotype.

2. The illustrations in Yang et al. (1996: photo no. 80 on p. 785) and Ying (1998: 62, photo 561) are labelled as B. formosana but are almost certainly of this taxon.

3. Boehmeria pilosiuscula is distinctive in its female and bisexual inflorescence-bearing axes short and interruptedcongested with large often densely congested clusters of tightly congested female flowers, its male flowers mainly found in a few small male clusters only at the apex of these axes, its fruiting perianth broad obconical-truncate, its mixed stem indumentum of sparse relatively long curved hairs and dense minute pubescence spreading at right angles to the stem and its leaves small and thin-textured, often markedly asymmetrical. It is probably under-collected, only one collection have been seen from each of North and South India, Sumatera and Borneo, so the material seen may not represent its complete distribution.

4. Two almost allopatric regional varieties are recognised. Var. pilosiuscula (north-eastern and south-eastern India, Sri Lanka, Burma, Philippines, Indonesia) and var. suffruticosa ( Burma, Thailand. China). The typical variety at its extreme presents a rather different appearance to that of var. suffruticosa but is rather variable. Var. suffruticosa shows little range of variation but forms intermediate between the two occur in Taiwan, Hainan, Thailand and Jawa. See detailed discussion under var. pilosiuscula (Note 3).

5. Boehmeria listeri (sympatric, Himalayas and Burma) also has mixed indumentum (but the minute hairs are smaller and denser giving the whole plant a grey tinge), leaves asymmetrical (but relatively narrower and usually longer) and fruiting perianth obconical (but not apically flattened); it differs also in inflorescence-bearing axes usually longer, the bisexual (and female) ones mostly with several long branches at the base (rather than unbranched) and male flowers mainly in the lower part of the axis or abundant throughout its length.

6. Only B. ourantha (partly sympatric in Himalayas and Burma) and B. yaeyamensis (allopatric, maritime, Ryukyu Islands) also have male flowers similarly arranged in the upper parts of mainly female axes rather than below the female (on lateral male branches or in entirely male axes in lower leaf axils). Boehmeria yaeyamensis also has mixed stem hairs, small leaves and rather short thick axes with densely congested female clusters but is not otherwise similar, easily distinguished by its leaves ± symmetrical, truncate to cordate, thick-textured and even broader with few rounded teeth. Boehmeria ourantha has stem hairs uniform, dense long conspicuous and golden, leaves larger, symmetrical, truncate or cordate, marginal teeth larger and inflorescence-bearing axes long.

7. Without male flowers, forms of B. pilosiuscula with large thick-textured leaves can be confused with the partly sympatric B. rugosissima and the two are apparently sometimes found growing together (see detailed discussion in Note 4 under B. rugosissima ).

8. When male flowers are not present, B. virgata subsp. macrophylla var. scabrella and forms of B. pilosiuscula with less markedly asymmetrical leaves can readily be confused due to the similar leaf shape and short erect inflorescence-axes with crowded clusters. The two are partly sympatric (in northern India, Southern China and Jawa). However, the mixed stem indumentum gives a distinctive appearance discernible by the naked eye; var. scabrella has ± uniform usually stiff straight closely-adpressed or half-adpressed hairs and even forms with some hairs softer and slightly curved clearly lack the minute indumentum. Female flowers in var. scabrella are obovoid, tapering towards their apex such that not even large crowded female clusters appear like a solid mass, rather than obconical-truncate with a broad apex. In var. scabrella female clusters are also mostly smaller, up to c. 4 mm diam (rather than 4–7 mm) and male clusters are always on separate branched axes or short branches at the base (rather than a few clusters along the apical part) of an otherwise female axis. Fruiting perianth in B. virgata subsp. macrophylla var. scabrella is very varied including ovoid ± unwinged forms and flattened spindle-shaped with a wing more or less surrounding the achene, rather than consistently obtriangular with a flattened apex. Leaves in B. virgata subsp. macrophylla var. scabrella are also often broader (length often only 1.3–1.5 × width). Boehmeria virgata subsp. macrophylla var. scabrella differs from var. suffruticosa additionally in longer and broader marginal teeth, 1.5–2 by 3–6 mm (rather than ≤ 1.5 by 2 mm), and much longer female axes (at least 5 cm long). It is less easy to distinguish from var. pilosiuscula but its mainly male axes are many-branched and frequent and male flowers are subsessile rather than usually clearly pedicellate.

Key to varieties

1. Female and bisexual axes with clusters congested into continuous mass ≤ 2 mm long and lower 0.5–1 mm part of axis often naked (whole axis 1–2(–3) mm long), flower-bearing part ≤ 2 cm; leaves never bullate, always thin-textured, marginal teeth 1(–1.5) mm long, usually up to 30 either side; entirely male branched axes absent. — Burma; Thailand; China.......................... b. var. suffruticosa

Figures

Map 40 Distribution of Boehmeria pilosiuscula (Blume) Hassk. var. pilosius­ cula (●) and intermediates between B. pilosiuscula var. pilosiuscula and var. suffruticosa (ä).

Map 41 Distribution of Boehmeria pilosiuscula (Blume) Hassk. var. suffruticosa Acharya, Friis & Wilmot-Dear.

Fig. 38 a–i: Boehmeria pilosiuscula (Blume) Hassk. var. pilosiuscula. a. Habit of stem with bisexual and female inflorescence-bearing axes; b. lower node of stem with branched male inflorescence-bearing axis; c. detail of stem showing two kinds of spreading hairs; d. leaf; e. leaf, detail of abaxial surface; f. detail of stem and stipule; g. upper part of bisexual inflorescence-bearing axis with congested female flower-clusters (inflorescences) below and few-flowered male clusters (inflorescences) at apex; h. male bud; i. fruiting perianth. — j: Boehmeria pilosiuscula var. suffruticosa Acharya, Friis & Wilmot-Dear. Habit of stem with bisexual and female inflorescence-bearing axes (a, e, f, h: Sinclair 10053, K; b: de Vriese s.n., L; c, d: Kostermans 18171, K; g: Henry 12370, K; i: Gammie 190, K; j: Henry 12696, K). — Scale bars: a, b, d, j = 2 cm; c, g-i = 1 mm; e, f = 2 mm.