Boehmeria zollingeriana Wedd.

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 : 119-120

9. Boehmeria zollingeriana Wedd. — Fig. 8 ; Map 10 , 11

Boehmeria zollingeriana Wedd. (1854) 201. ― Type: Zollinger 2765 (holo P; iso BO, G, U), Indonesia, Jawa [Java], Bandowosso Prov., Warmagen .

Boehmeria diversiflora Miq. in Zollinger (1854 June) 101, 104 ― Type: Zollinger 2765 (iso BO, G, U), Indonesia, Jawa [Java], Bandowosso Prov., “ad rupes prope Warringin”. – See Note 1.

Shrub, sometimes scrambling, 3(–4) m tall; ultimate branches slender, up to 0.5 mm diam, glabrous or sometimes hairy, hairs sparse fine weak ± spreading; drying often red-brown. Stipules lanceolate, 7–11(–15) by 1–1.5(–3) mm, fairly thick-textured. Leaves opposite (but often subopposite or alternate close to apex, especially those just below terminal inflorescence-bearing axes), not or moderately dimorphic with length of ‘larger’ leaves up to 2 × that of ‘smaller’ and ‘larger’ leaves often also relatively wider, symmetrical or with apex slightly sideways-curved, ovate to narrowly ovate (to deltate), small to large 7–19 by 2–14 cm, length 1.3–4 × width; margin crenate or bluntly, rarely ( China) sharply, serrate, teeth relatively few ether side, 8–20(–30), distinct, 0.5–2(–4) by 4–11 mm, becoming indistinct or absent in proximal quarter of lamina; leaf apex gradually long-attenuate to indistinctly long-acuminate or abruptly short-acuminate; base rounded to slightly cuneate, truncate or slightly cordate, usually slightly asymmetrical; basal veins extending to middle of lamina or on adaxial side sometimes into distal third, upper lateral veins 2–4(–5) either side, on abaxial side usually arising slightly lower, lowermost often arising in proximal third of lamina, these and coarser ± scalariform tertiary venation (especially veins arising between basal vein and margin) often fine-prominent abaxially; texture very thin-chartaceous, rarely thicker and leaves slightly bullate, drying dark brownish black, lighter brown below, adaxial surface usually glabrous and ± shiny, rarely ( Thailand) with an occasional minute adpressed single hair in centre of some areoles, abaxial surface with extremely sparse adpressed hairs only on veins; petiole of ‘larger’ leaf variable with respect to leaf-size but relatively short 0.1–0.25 × lamina length, relatively even shorter on ‘smaller’, glabrous or sparsely hairy like the stem. Male flower­clusters simple axillary, up to 15 mm diam, sessile with 5 –30 flowers, these loosely arranged, long-pedicellate; female clusters borne along ± leafless axes (occasionally with 1–2 pairs of leaves in lower half, these much smaller and narrower than main-stem leaves and often alternate), axes terminal and 1 per axil in upper axils, glabrous or very sparsely spreading-hairy, drying red-brown, 20–40 cm long, sometimes pendulous and unbranched, more often erect and robust (sometimes pendulous towards apex) with basal third or half of main axis often naked (i.e., no flower-clusters or leaves present), much-branched in upper half with lateral branches often equalling main axis and often 1-branched again, these ultimate branches also long; bracts minute, inconspicuous, <1 mm long; clusters well-spaced, 2 – more than 10 mm apart, in flowering state small, up to 3 mm diam, with 10–30 flowers, densely congested; bracteoles narrowly linear-oblong, sometimes conspicuous, 0.5–1 mm long. Male flowers 5– 6-merous with a conspicuous pedicel 5–8 mm long, mature buds depressed-globose, c. 2 mm diam, with conspicuous dorsal thickening on each lobe, glabrescent or with very sparse hairs near apex, these very fine. Female flowers up to 0.5 mm long, stigma variable in length but often minute, curved, 0.5–1(–1.5) mm. Fruiting perianth only 0.5–1 by 0.4–0.8 mm, broadly obovoid or ellipsoid with minute beak, markedly dorsiventrally flattened with marginal rim or distinct thick-textured marginal wing, with inconspicuous hairs, these very sparse, short, fine; achene filling most of fruiting perianth.

Distribution ― South-eastern India and from Burma to south-western China (including Taiwan), Thailand, Laos, Vietnam, Indonesia (Jawa) and Philippines (Luzon).

Habitat & Ecology ― Evergreen and deciduous forest, maritime forest and open shrubby areas; sea level– 1400 m altitude.

Conservation status ― Least Concern (LC). The species is known from at least 200 collections, many of which are recent, and it occurs in many widely scattered location, and in a wide range of habitats, with an EOO of 6 683 520 km 2.

Notes ― 1. Boehmeria zollingeriana was independently described in the same year as B. diversiflora and based on a different duplicate of the same collection; the exact month of publication (and therefore priority) of both names cannot be ascertained but B. zollingeriana is maintained here as it is the name in current use.

2. This species is normally easily recognisable. It is unique in the genus in having male and female clusters very differently arranged, female on specialised leafless axes, male ones simple axillary; male flowers are also unique in the Old World in being 5–6-merous (rather than 4-merous) and in pedicels being many times longer than in any other species. Axillary clusters of pedicels usually remain long after male flowers have fallen and are good distinguishing character from all other species even in fruiting specimens. Its glabrous appearance in most parts, stems and inflorescence-axes drying red-brown, inflorescence-bearing axes long but robust, erect, ± branched, the fruiting perianth often very small and broad and leaves ± glabrous, shiny, usually with rounded base, are also useful distinguishing characters.

3. Boehmeria leptostachya which was hitherto confused with this species, has similarly red-tinged stems, petioles and axes but differs markedly in its male flowers ± sessile and borne along the slender leafless bisexual axes and in its leaves ± elliptic, abundantly minute-hairy adaxially with basal veins extending nearer to lamina apex and lowermost lateral veins arising nearer apex.

4. Specimens consisting only of the apical part of a branch and therefore lacking the distinctive axillary male clusters can be mistaken for B. virgata subsp. virgata var. virgata (sympatric only in Jawa) whose wide range of variation in leaf shape, -texture and indumentum overlaps. However, B. virgata never has alternate leaves even in the upper part of stems.

5. Two varieties are recognised, partly sympatric ( Burma, China, Thailand and Indonesia (Jawa )). Var. zollingeriana is also known from southern India (from only one collection, suggesting that it is under-collected) and occurs in both forest and more open habitat. It has leaves broadly ovate to deltate with relatively long, rounded teeth, female axis with clusters throughout length, often unbranched and very long (up to 40 cm), ± pendulous. Var. podocarpa is also known from Taiwan and the Philippines and appears to be restricted to forest; it has leaves narrowly ovate, with shallow, sometimes acute teeth, female axes generally shorter (up to 25 cm), much-branched and erect (except for pendulous tip) with clusters often absent from lower quarter or half of axis.At the extremes of their range of variation the two varieties look very different, but forms impossible to assign to either variety, with leaves shallowly crenate as in var. podocarpa but of intermediate length and proportion have been seen from Indochina, Philippines and Jawa. Yahara (1981: 13) noted this variation in leaf proportions and margin in Thai material. In Taiwan var. podocarpa sometimes has fine weak hairs on young stems and petioles; the glabrous more widespread forms were recognised by Chen et al. (2003) as var. blinii (H.Lév.) C.J.Chen , but indumentum in Taiwan ranges from (rarely) abundant to sparse to ± absent and no formal distinction is possible.

6. Leaves of var. podocarpa are rather like those of the partly sympatric B. hamiltoniana in shape but drying dark brownish black rather than green, usually shinier, never membranous and sometimes thick-chartaceous and upper veins are more numerous spaced throughout length rather than only in distal half.

7. Var. podocarpa is easily distinguishable from most other species of Boehmeria (even when the diagnostic male clusters are absent) by leaves narrow, attenuate, ± glabrous, rather shiny with relatively numerous lateral veins throughout length and female axes much-branched erect with a long naked lower portion. Var. zollingeriana is less distinctive with its broader, acuminate leaves with lateral veins fewer, often all in distal half of lamina, and female inflorescence-bearing axes often pendulous, unbranched or few-branched, and has been confused with broader cordate forms of the widespread B. virgata subsp. macrophylla , which, however, has leaves dentate rather than crenate always with inconspicuous hairs adaxially (rather than shiny ± glabrous or with occasional scattered hairs), and the stem is hairy at least near its apex.

8. Var. podocarpa is also often vegetatively somewhat similar to Pouzolzia sanguinea var. sanguinea , and can be misidentified when flowers and fruiting perianths are absent. Pouzolzia sanguinea differs in flower-clusters all similarly arranged, mostly axillary and often bisexual; male flowers are subsessile and female flowers are large (0.8–1.3 mm diam) with stigma often very long (1.5–5 mm); the fruiting perianth is large (1.5–2 mm diam), ribbed but not flattened or winged.

Key to varieties

1. At least lower leaves broadly ovate or deltate-truncate with length only up to 1.4 × width and apex abruptly short-acuminate; female inflorescence-bearing axes often pendulous, (20–) 30–40 cm long, with clusters throughout most of length, few-branched or sometimes entirely unbranched..................................... a. var. zollingeriana

Figures

Map 10 Distribution of Boehmeria zollingeriana Wedd. var. zollingeriana.

Map 11 Distribution of Boehmeria zollingeriana Wedd. var. podocarpa (W.T.Wang) W.T.Wang & C.J.Chen (●) and intermediates between var. zollingeriana and var. podocarpa (ä).

Fig. 8 a–c: Boehmeria zollingeriana Wedd. var. zollingeriana. a. Habit of plant with female inflorescence-bearing axes; b. leaf; c. winged fruiting perianth. — d–h: Boehmeria zollingeriana var. podocarpa (W.T.Wang) W.T.Wang & C.J.Chen. d. Habit of plant with axillary male flower-clusters (inflorescences) on main stem and branched inflorescence-bearing axes with female clusters (inflorescences); e. detail of stem with stipule and pair of male flower-clusters (inflores- cences), flowers pedicellate; f. male bud; g. detail of female axis with three flower-clusters (inflorescences); h. unwinged fruiting perianth (a: Winit 1422; b, c: Henry 12541A; d–f: Ford 33; g, h: Collett 922; all K). — Scale bars: a = 5 cm; b, d = 2 cm; c, f, h = 1 mm; e, g = 2 mm.