Boehmeria helferi Blume

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 : 112-113

7. Boehmeria helferi Blume — Fig. 6 ; Map 5

Boehmeria helferi Blume (1857) 201. ― Type: Helfer 4585 (holo W;iso CAL, K), Burma, Tenasserim, 13 May 1838.

Subshrub (height not clear from the scarce material); ultimate branches 1–1.5 mm diam, with sparse inconspicuous adpressed hairs, soon robust and glabrous. Stipules broadly or narrowly triangular, 4–8 by 1.5–2 mm, thin-chartaceous with scattered hairs outside. Leaves opposite, dimorphic in petiole length (‘larger’ petiole at least 2 × length of ‘smaller’) and sometimes slightly in lamina size, all leaves broadly ovate, symmetrical, 5–10 by 3.5–6 cm, length (1.4–)1.8 × width, margin deeply serrate with 15–25 teeth, these acute, up-curved, 3–4 by 3–4 mm; leaf apex abruptly acuminate consisting of one long tooth with 1–2 lateral teeth at base; base rounded and slightly cordate; basal veins extending slightly into distal half or to distal third, upper lateral veins c. 2 each side, similarly arranged but hardly distinct from coarser tertiary venation, lowermost arising near or below middle of lamina, inconspicuous adaxially, finely prominulous abaxially; texture very thin-chartaceous, adaxial surface with sparse fine inconspicuous adpressed hairs; abaxial surface with longer hairs and also minute and often spreading hairs; petiole long compared to lamina length, on ‘larger’ leaf often almost equalling lamina, 3–8 cm long. Flower­clusters axillary, large, 4–5 mm diam, with more than 50 flowers, these densely crowded, all flowers female or clusters with a few male ones; bracteoles narrowly elliptic to obovate, ± acute, ≤ 0.3 mm. Male flowers 4-merous, depressed-globose, mature buds large, c. 1.8 mm diam, with slight dorsal thickening and sparse adpressed hairs. Female flowers ellipsoid to or ovoid with short beak, 0.8–1 by c. 0.5 mm, slightly laterally flattened; stigma long, 1.5–2 mm. Fruiting perianth very small, c. 1 by 0.5 mm, ovoid to ellipsoid, moderately flattened and with slight marginal wing and broad beak. Achene ± filling fruiting perianth, fawn.

Distribution ― India (West Bengal), Burma (Tenasserim).

Habitat & Ecology ― No details in original description, presumably coastal rainforest.

Conservation status ― Critically Endangered (CR). The species is known from only two collections, both from the 1830s, the type (from Tenasserim in Burma) and a collection from India, West Bengal, Kolkota [Calcutta], 1836–1838, Helfer 125 (K). Since these two collections are from localities far apart, both regions where major habitat loss has occurred (one being within the urban expansion of Kolkota), and the AOO is only 8 km 2, we propose the IUCN category Critically Endangered CR 2Bab(iii) .

Note ― A species of very restricted distribution unique among the Old World taxa in its combination of opposite leaves and axillary flower-clusters. Its leaves which are large, broad and deeply-up-curved-toothed are rather similar to smaller forms of B. japonica (which differs in marginal teeth progressively markedly larger towards leaf apex) and also similar to some forms of B. clidemioides . Both these taxa differ from it in inflorescence architecture, flower-clusters being borne in B. japonica on specialised leafless axes and in B. clidemioides mostly on short lateral axes which are partly-leafless.

Figures

Map 5 Distribution of Boehmeria didymogyne Wedd.(▲), B. helferi Blume (●) and B. manipurensis Friis & Wilmot-Dear (■).

Fig. 6 Boehmeria helferi Blume. a. Upper part of stem showing axil- lary flower-clusters (inflorescences); b. leaf; c. leaf, detail of adaxial surface;d. detail of abaxial surface; e. stipule;f. pair of axillary bisexual flower-clusters (inflorescences);g, h. female perianths of different form (from same plant) (a–e, g, h: Helfer 4585; f: Helfer 125; all K). — Scale bars: a = 2 cm; b = 1 cm; c-e, g, h = 1 mm; f = 2 mm.