VIETNAM. Thua Thien Hue Province, Bach Ma National Park, edge of evergreen forest along stream, 16°13'36.70"N, 107°51'07.22"E, alt. 414 m, 24 May 2015, with flowers, Tagane S., Toyama H., Yahara T., Ngoc Nguyen, Chinh Nguyen, Okabe N. V2677 (holotype KYO!, isotypes BKF!, DLU!, FU!, P!, VNM!, the herbarium of Bach Ma National Park!).

Callicarpa bachmaensis is distinguishable from the other species of Callicarpa by a combination of its liana habit, white flowers and narrowly elliptic to narrowly lanceolate, entire, occasionally subequal leaves. Callicarpa angusta Schauer, endemic to Philippines, and C. angustifolia King & Gamble, distributed in China, Cambodia, Thailand, Vietnam, and Peninsular Malaysia, resemble to C. bachmaensis in possessing narrowly elliptic leaves. However, they differ from C. bachmaensis in having a shrubby habit and serrate leaves. Additionally, C. angusta differs in having hairy corollas, and C. angustifolia differs in having larger leaves (more than 9 cm long in C. angustifolia vs. less than 9 cm long in C. bachmaensis) and larger corollas (ca. 3 mm long vs. 2–2.2 mm long).

Liana-like small tree, ca. 3 m tall. Branches sweeping with gradual curve and overhanging distally. Twigs with a dense indumentum of short plumose or dendroid brown hairs, slightly 4-angular when young, later becoming terete, woody and glabrous, lenticellate; internode 8.7–13 cm long in main stems, 1.4–3 cm long in axial ones. Leaves opposite, occasionally subequal; blades narrowly elliptic to narrowly lanceolate, (2.6–)5–8 × (0.4–)0.8–2 cm in larger leaves, 1.1–4 × 0.2–1 cm in smaller ones, base acute to cuneate, apex acuminate, margin entire, upper surface with short stellate hairs or sometimes almost glabrous, also with small yellow sessile glands and a few larger sessile glands, lower surface densely covered with white stellate or sometimes pale brownish fringed peltate scale-like hairs and a few larger sessile glands, chartaceous to subcoriaceus, green and slightly lustrous above, white hairy below; midrib slightly sunken above, prominent below, secondary veins 6–10 pairs, prominent below, tertiary veins scalariforming-reticulate; petioles 0.8–1.1 cm long, with indumentum as branches. Inflorescence axillary, cymose, entirely covered with indumentum as branches, peduncles 0.8–1 cm long; bracts linear, 1.5–2 mm long; pedicels ca. 0.5 mm long. Calyx cup-shaped, 1–1.5 mm long with 4 (or 5) shallow lobes, outer surface covered with stellate or short dendroid hairs and small yellow sessile glands, inner surface almost glabrous. Corolla white, 2–2.2 mm long, divided into four lobes, tube ca. 1 mm long, lobes oblong-ovate, <1 mm long, apex rounded, outer surface with yellow sessile glands, inner surface almost glabrous. Stamens 4, ca. 1 mm long exerted from corolla, filaments 2.5–3 mm long, glabrous, anthers elliptic, ca. 1 mm long, with many yellow sessile glands near connectives, dehiscing through longitudinal slits. Stigma capitate, style ca. 6 mm long, glabrous. Fruits drupaceous, spherical, 2.5–3 mm in diameter, dark purple, sparsely covered with stellate hairs.

Vietnam. 20 June 1976, with fruits, Ly Quoc Anh 106 (HN!); Lao Cai Province: Liem Phu, Van Ban, 10 June 2008, with flowers, Binh N.Q. & Cuong D.D. VN1985 (HN!); Quang Nam-Da Nang Province: Hà ra, Giăng village, 13 July 1986, with fruits, LX-VN 2958 (HN!); Vinh Phuc Province: Me Linh Biodiversity Station, Ngoc Thanh Commune, 24 Oct. 2001, with fruits, Phuong et al. 4611 (HN!).

Flowering specimens were collected in May and June; fruiting in June, July, and October.

VIETNAM: Northeast (Lao Cai and Vinh Phuc Province) and Central coast (Thua Thien Hue, Quang Nam and Da Nang Province) (Fig. 3). In the type locality, Bach Ma National Park, Thua Thien Hue Province, a small population was found at the edge of humid broad-leaved evergreen forest along a stream, at altitude ca. 400 m, in which Dipterocarpus hasseltii Blume (Dipterocarpaceae), Croton argyratus Blume (Euphorbiaceae), Vitex axillariflora (Merr.) Bramley (Lamiaceae), Beilschmiedia henghsienensis S. K. Lee & Y. T. Wei (Lauraceae), Litsea balansae Lecomte (Lauraceae), Heritiera augustata Pierre (Malvaceae), Syzygium diospyrifolium (Wall. ex Duthie) S. N. Mitra (Myrtaceae), S. siamense (Craib) Chantar. & J. Parn. (Myrtaceae), Adina pilulifera (Lam.) Franch. ex Drake (Rubiaceae) dominate.

Figure 1. 

Callicarpa bachmaensis Soejima & Tagane, sp. nov. A Branch apex B Flowering branch C Abaxial surface of lamina D Inflorescences E Twigs and base of petiole, F Infructescence [Binh & Cuong VN1985 (HN). Scale bar E = 5 mm].

Figure 2. 

Callicarpa bachmaensis Soejima & Tagane, sp. nov. A Flowering branch B Stellate and dendroid hairs on calyx (left three) and lower surface of leaves (right) C Abaxial surface of lamina D Flower with the corolla dissected to show filaments and style E Fruit. Materials: Tagane et al. V2677.

Figure 3. 

Distribution of Callicarpa bachmaensis Soejima & Tagane. Black triangle: type locality in Bach Ma National Park; white triangle: other collection sites in Vietnam.

Tagane et al. V2677: LC120829 (rbcL), LC120830 (matK).

The specific epithet bachmaensis reflects the name of the locality where the type specimen was collected.

Data Deficient (DD). Callicarpa bachmaensis is collected from north and central Vietnam. In the type locality, Bach Ma National Park, the number of individuals is likely stable, but at present we have no reliable information on its abundance and range. Further investigations are needed to accurately assess its status in the natural habitat.