Boehmeria splitgerbera Koidz.

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 : 195-196

29. Boehmeria splitgerbera Koidz. — Fig. 36a–f ; Map 38

Boehmeria splitgerbera Koidz. (1926) 345. ― Splitgerbera japonica Miq. (1840) 134, t. 14, f. A–K, non B. japonica (L.f.) Miq. (1867). ― Type: Unknown collector, cultivated from Japan s.n. (iso K, WU), “ Japan, E, cult in horto prope Tjpannas”.

Boehmeria biloba Miq. in Zollinger ([June] 1854) 100, nom. illeg. superfl., based on Splitgerbera japonica Miq. (1840: 134, t. 14). – See Note 1.

Boehmeria bifida Blume (1857) 222, nom. illeg. superfl., based on Splitgerbera japonica Miq.

Robust herb, 0.5–1 m tall, with 1–several stems arising from woody rootstock, each stem partly prostrate in lower part and unbranched or little-branched; ultimate stems robust, 2–2.5 mm diam, with hairs of 2 kinds, abundant stiff long curved hairs mixed with sparse short soft spreading ones. Stipules narrowly triangular, c. 10 by 2 mm long. Leaves opposite, not or slightly dimorphic in size only, very variable in shape and often misshapen, elliptic, broadly ovate to obovate or even orbicular or more or less spathulate but markedly asymmetrical with width of one half up to 1.5 × other half, medium or large, 8–14 by 5–9 cm, length (1–)1.2–2 × width; margin shallowly dentate, teeth 30–40 either side, outward-pointing, indistinct or up to 1.5 by 2–6 mm long; leaf apex very variable, broadly acute to rounded, abruptly short-acuminate or asymmetrically bilobedbi-acuminate; base narrowly long-cuneate to broad short-cuneate, rounded or even truncate; basal veins rather straight, usually extending well into distal third of lamina or almost to tip especially in non-lobed leaves; upper lateral veins 2(–3) on one side, 4–5 on other and often arising in lower half of lamina, these and tertiary reticulation finely prominent abaxially; texture thickly chartaceous to thinly coriaceous, leaves often bullate; adaxial surface with scattered hairs like those on stem; abaxial surface with abundant hairs like stem; petiole short but variable, 2–4 cm long, 0.15–0.3 × lamina length. Flower­clusters borne on leafless axes, unbranched, 1 per axil, male axes 10–16 cm, female 4–8 cm long, some axes with both sexes; bracts narrowly triangular 3 by 1.5 mm with long-acute or acuminate apex; male clusters usually well-spaced, 2–3 mm diam, with 5–10 loosely-arranged flowers; female clusters often crowded or contiguous, 4–5 mm diam, with 50–100 densely crowded flowers; bracteoles inconspicuous, narrowly triangular or linear, c. 1/3 of flower length, 0.5 mm long. Male flowers 4-merous, sessile or subsessile, mature buds globose, c. 1 mm diam, dorsal appendage prominent up to 0.2 mm long, hairs dense, long. Female flowers narrowly oblong-ovoid, up to 1.5 by 0.3 mm; stigma 1–1.5 mm long. Fruiting perianth up to 1.8 by 1 mm, very variable in shape, ovoid or obovoid-oblong usually tapering into long-pedicellate basal portion, often rather inflated at apex and usually markedly laterally flattened except for small central part containing achene, densely hairy. Achene ellipsoid, c. 0.5 by 0.4 mm.

Distribution ― Japan (Hokkaido, Honshu, Kyushyu, Izu Islands, Bonin Islands), South Korea.

Habitat & Ecology ― A pioneer species on volcanic rocky cliff faces along seashore, roadsides; sea level–1000(–2000) m altitude.

Conservation status ― Data deficient (DD). Its particular habitats are not currently threatened, and it is known from over 50 collections but the scarcity of recent collections is puzzling.

Notes ― 1. Boehmeria biloba Miq. in Zollinger ([June] 1854: 100), nom. superfl. illeg., based on Splitgerbera japonica Miq. (1840) 134, t. 14, the epithet of which should have been adopted, as the combination B. japonica (L.f.) Miq. had not yet been proposed in 1854. The combination B. biloba had already been suggested by Weddell (in a preprint from March 1854, p. 27 (preprint of Weddell 1854: 199), similarly based indirectly on the above-mentioned S. japonica Miq. (1840) , which Weddell erroneously, but unambiguously, referred to as S. biloba Miq. (with full reference to page and illustration of S. japonica , but with the wrong name, S. biloba ), possibly confused by the presence of the nomen nudum Urtica biloba Siebold on some early collections of this plant. Hence the name B. biloba cannot be used.

2. Boehmeria splitgerbera is easily distinguished especially in its leaves, which are thick-textured (especially on sea-shores), ± bullate, fairly broad, but often rather abruptly cuneate at the base, shallowly and finely dentate, leaf shape often very varied even on a single plant but usually at least some leaves bilobed, others often misshapen and/or obovate; veins are robust and rather straight, basal lateral veins running nearly to tip of lamina, often bifurcated near apex and with many rather robust tertiary veins running towards the margin. Its indumentum of mixed long coarse and short spreading hairs is also distinctive. Spreading stems and height only up to 1 m tall are features retained in cultivation (Yahara 1983a: 236 and appears to be adaptation to its habitat).

3. Boehmeria yaeyamensis (allopatric, Ryukyu Islands) is somewhat similar in habit, indumentum, leaf texture and densely crowded female inflorescence-bearing axes but does not have misshapen or bilobed leaves, bifurcate veins or winged or ± pedicellate fruiting perianths; both are maritime species of very restricted distributions.

4. A range of entities of obscure identity exists in Japan and South Korea (Jeju ‘Quelpart’ Island) having some or all of the following characters distinctive to B. splitgerbera (2 kinds of hairs; leaves misshapen or slightly bilobed at apex; lateral veins bifurcated near apex; reticulation prominent), but leaf margin with fewer, larger, teeth, leaf texture also sometimes thin. As discussed in the introduction section, Yahara (1983a) showed populations of this nature in Izu (Honshu) to be polyploid, apomictic and morphologically distinct from one another. He suggested that they originated through hybridisation of B. splitgerbera with either an unknown parent (the thickerleaved forms) or the B. japonica complex (the thinner-leaved forms). Some of the thin-leaved material is, however, so similar in leaf shape to B. holosericea that this is a more likely parent (see further under B. holosericea , Note 8). The types of the names in the following Note, some of which were mentioned by Yahara (1983a, 1984a), fall within this range of variation.

5. Material intermediate between B. splitgerbera and other taxa.

Boehmeria arenicola Satake (1936) 499. ― Type: Satake 3557 (holo TI; iso TI), Japan, Honsyu, Sagami, 16 Oct. 1935.

Boehmeria arenicola Satake var. awana Satake (1936) 500. ― Type: Satake 3566 (holo TI), Japan, Honshu, Awa Prov.

Boehmeria dura Satake (1936) 529. ― Type: Satake 3587 (holo TI; iso TI), Japan, Honsyu, Izu, 5 Sept. 1935.

Ohba (2006: 107) accepts B. dura as the correct name for a natural hybrid involving B. splitgerbera and B. japonica .

Boehmeria izuosimensis Satake (1936) 532. ― Type: Y. Jotani s.n. (holo TI), Japan, Honsyu, Izu Islands , Osima Island, 9 Sept. 1931.

Ohba (2006: 107) accepts B. izuosimensis as the correct name for a natural hybrid involving B. splitgerbera and B. japonica .

Boehmeria kiyozumensis Satake (1936) 497. ― Type: H. Hara s.n. (holo TI), Japan, Honsyu, Awa, 5 Nov. 1934.

Boehmeria tenuifolia Satake (1936) 501. ― Type: Y. Momiyama 529 (holo TI), Japan, Honsyu, Sagami, 3 Nov. 1934.

Boehmeria tenuifolia Satake forma conferta Satake (1936) 501. ― Type: Momiyama s.n. (holo TI), Japan, Honsyu, Sagami, 10 Nov. 1935.

Boehmeria tenuifolia Satake var. nigricans Satake (1936) 501. ― Type: Satake 3572 (holo TI), Japan, Honsyu, Izu province, 4 Sept. 1935.

Boehmeria pannosa Nakai & Satake in Satake (1936) 510; Nakai (1936) 150. ― Type: Nakai & Maekwa s.n. (holo TI, n.v.; photo in Satake 1936), Japan, Honsyu, Suo, 22 July 1935.

Figures

Map 38 Distribution of Boehmeria splitgerbera Koidz. (●) and B. yaeya­ mensis Hatus. (Ê).

Fig. 36 a–f: Boehmeria splitgerbera Koidz. a. Habit of stem with inflorescence-bearing axes, in lowermost part of plant pendulous male axes, above erect, congested female axes; b–d. leaves from different plants; e. male bud; f. fruiting perianth. — g–m: Boehmeria yaeyamensis Hatus. g. Upper part of stem showing congested erect inflorescence-bearing axes; h. detail of stem showing stipules and base of paired axillary inflorescence-bearing axes concealing petiole base; i. leaf, detail of abaxial surface; j. portion of inflorescence-bearing axis showing congested female flower-clusters (inflorescences) and bracts; k. male bud; l, m. fruits of different form from same plant (a, f: Furuse 26669; b, e: Hort Kew s.n.; c: Furuse 28436; d: Koyama 268; g–j: Furuse 4213; k: Furuse 3199; l, m: Furuse 4148; all K). — Scale bars: a = 5 cm; b, g = 2 cm; c, d = 1 cm; e, f, k–m = 1 mm; h-j = 2 mm.