Boehmeria macrostachya var. rotundifolia, 2013

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 : 166-168

j. var. rotundifolia (D.Don) Friis & Wilmot-Dear , comb. nov. — Fig. 26 ; Map 27

Basionym: Boehmeria rotundifolia D.Don, Prodromus Florae Nepalensis (1825) 60. ― Boehmeria macrophylla Hornem. var. rotundifolia (D.Don) W.T.Wang in Wang & Chen (1995) 337. ― Type: Hamilton s.n. (lecto BM; left-hand specimen only, lectotype selected here), Nepal, Upper Nepal, Suembu. – See Note 2.

Woody-based herb, 1–2 m tall. Stems with abundant fine hairs 0.2–0.4 mm long, close-adpressed, inconspicuous, and sometimes also sparse longer (c. 1 mm long) hairs, spreading, curved, coarser. Stipules 7–10 mm, with long hairs on midrib and short adpressed hairs elsewhere like those on the stem. Leaves broadly elliptic to almost orbicular, small or fairly large, 5–20 by 3.5–16 cm, length 1–1.25(–1.4) × width; marginal teeth (20–)25–30 either side, (2–)2.5–5 by 2.5–7 mm, longer and relatively broader on larger leaves and with width 1–1.25(–2) × length, markedly up-curved and usually increasingly so towards leaf apex; leaf apex with abrupt distinct narrow acumen (5–) 15–20 mm long, mostly only c. 2 mm wide but sometimes widening to 3 –5 mm close to its base, consisting mostly of a single long tooth but with 1(–2) pairs of teeth close to base; base broadly cuneate to broadly rounded (rarely ± truncate); texture thin-chartaceous, adaxial surface with sparse adpressed (rarely curved) hairs like those on the stem, abaxial surface with sparse fine hairs mostly restricted to veins, these half-adpressed, straight, those on main veins the longest, rarely with shorter finer less sparse hairs on whole surface; petiole variable but often relatively long 0.4–0.8(–1) × lamina length, hairy like the stem. Inflorescence-bearing axes ± erect or drooping, male axes 5–13 cm long, female ones 8–14 cm long, sometimes unbranched or with a few long branches near base or male ones mostly (female rarely) with short (2–3 cm) branches throughout most of length, sexes sometimes on same axes with male clusters on lateral branches; clusters spaced (2–) 3–5 mm apart or sometimes, especially female clusters, ± contiguous in parts of the axis, male clusters with up to c. 10 flowers, female with usually 30–40 flowers. Fruiting perianth rather small ≤ 0.8 by 0.4–0.5 mm, broadly ellipsoid with rounded base and without distinct beak, with abundant fine spreading hairs throughout. Achene ± filling fruiting perianth.

Distribution ― Eastern Himalayas: India (Sikkim), Nepal, Bhutan, Burma; south-western China.

Habitat & Ecology ― Open grassy areas and secondary vegetation around field-edges or amongst dense herbaceous vegetation, usually in moist places, rarely as successional regrowth in fire-damaged evergreen broad-leaved forest; (1600–) 2000– 3000 m altitude.

Notes ― 1. As discussed in detail under the species as a whole (see Note 5-viii), var. rotundifolia is distinctive in its leaves with terminal tooth long and tail-like and distal marginal teeth markedly in-curved; it is often rather similar to var. scabrella which has a slightly lower altitudinal range and occurs in forest and thickets. Only ten collections clearly referable to this variety have been seen, together with other material intermediate with var. macrostachya or var. scabrella ; therefore formal conservation status assessment is not meaningful. It occurs in locations along the Himalayas and the extension of this mountain range into southern China. It is not clear whether the open and often somewhat disturbed habitats in which it is often found are currently threatened by serious degradation.

2. As discussed under the species, most material of var. rotundifolia has only adpressed hairs on the stem; only the type from Nepal and the single collection seen from Bhutan have both kinds of stem-hairs like those found in var. canescens (but much sparser). The type specimen is ‘atypical’ in various characters, appearing to represent one extreme of the range of variation, with both kinds of hairs on the stem and is also the only material seen with rather slender inflorescence-bearing axes approaching those of var. canescens . This material consists of two detached stems, the left-hand one with the distinctive long terminal tooth (15 mm) but the right hand one less distinctive, with an acumen only c. 5 mm long; these are sufficiently dissimilar that they may have come from separate plants and we therefore select the left-hand specimen as lectotype.

3. As discussed under the subspecies as a whole (Notes 4, 6, 7), var. rotundifolia can be confused with B. ternifolia and narrow-leaved forms also with the sympatric but more widespread B. clidemioides and B. polystachya .

Figures

Map 27 Distribution of Boehmeria virgata (G.Forst.) Guillem. subsp.macrophylla (Hornem.) Friis & Wilmot-Dear var.rotundifolia (D.Don) Friis & Wilmot-Dear (●) and intermediates between B. vir­ gata subsp.macrophylla var. rotundifolia and other varieties (ä).

Fig. 26 Boehmeria virgata subsp. macrophylla var. rotundifolia (D.Don) Friis & Wilmot-Dear. a. Habit of stem with inflorescence-bearing axes; b. detail of stem with branched male inflorescence-bearing axes; c–e. leaves from different plants; f. leaf, detail of adaxial surface; g, h. leaf, detail of abaxial surface; i. detail of stem and stipules; j. detail of female inflorescence-bearing axis with flower-clusters (inflorescences) and bracts; k. fruiting perianth (a, h: Hooker s.n., K; b, e-g, i: Stainton 1622, BM; c, j, k: Kanai 6307118, BM; d: Nicholson 2359, BM). — Scale bars: a–e = 2 cm; f-j= 2 mm; k = 1 mm.