Acranthera burmanica Y. H. Tan & B. Yang, 2015

Tan, Yun-Hong, Yang, Bin, Li, Jian-Wu, Zhou, Shi-Shun, Lone, Shwe, Khaing, Kyi Kyi, Li, Ren, Huang, Jian-Ping & Sun, Hang, 2015, Acranthera burmanica, a new species of Rubiaceae from Kachin State, Myanmar, Phytotaxa 238 (1), pp. 92-96 : 92-95

Acranthera burmanica Y. H. Tan & B. Yang , sp. nov. ( Figs. 1–2 )

Type:— MYANMAR. Kachin State: Putao , Pananding. Understory shrubby herbs in tropical seasonal rain forests, 97º 51 ʹ 9.47 ʺ E, 27º 43 ʹ 28.99 ʺ N, alt. 1020 m, 30 Nov. 2014, Myanmar Exped. 313 (holotype HITBC 155761 ; isotype KUN 1262575 ) .

Diagnosis: Acranthera burmanica is similar to A. sinensis C. Y. Wu (1957:295) , differing from the latter by its stem and branches densely strigose throughout (vs. glabrescent when aged); ovate to ovate-lanceolate leaves (vs. elliptic or obovate); calyx distinctly shorter than corolla tube (vs. equal to corolla tube), calyx lobes lanceolate (vs. linear-lanceolate), apex attenuate (vs. acuminate); stipules triangular, apex acute not cuspidate (vs. broadly ovate to triangular, glabrescent, cuspidate); lower part of filaments connate into a tube (vs. free).

Shrubby perennial herbs, 50–80 cm tall, with tissues often turning black when dry. Stem terete, densely strigose throughout. Leaves opposite; petiole 1.5–4.5 cm, strigose to strigillose; leaf-blade thinly papery to membranous, ovate to ovate-lanceolate, 9.0–15 × 6.5–7.0 cm, adaxially sparsely hirsute to hispid, densely strigillose along midrib, abaxially sparsely puberulous denser along lateral veins, densely strigillose along midrib, base rounded, cuneate or obtuse, sometimes slightly unequal, apex attenuate or acute, margins ciliolate; lateral veins 9–10 on each side of midrib; stipules persistent, broadly ovate to triangular, 5.0–7.0 × 3.0–8.0 mm, densely villose, apex acute to acuminate, margins 3–4-glandular denticulate and ciliolate, the lower part connate into a short tube; Inflorescences terminal, pseudo-axillary, or axillary on short shoots, 1-flowered, short shoots abbreviated, 2.0–3.0 mm long, pilose; bracts in 2 whorls, outer bracts less than 2 mm long, inner bracts leaf-like, pink-red to dark-red, lanceolate, 6.0–8.0 × 3.0–4.0 mm, pubescent, midrib ridged with 1–2 lateral veins, margins entire and ciliolate; pedicel dark-red, 1–1.5 mm long, pubescent; bractlets lanceolate, dark-red, 8.0–9.0 × 2.0–3.0 mm, apex acute, pubescent outside and glabrous inside, margins entire and ciliate. Flowers 5-merous; calyx strigillose to strigose, glabrescent when aged; ovary portion cylindrical to obconical, dark-red, strigillose to strigose, 2.8–3 cm long; lobes slightly unequal, lanceolate, 1.7–2.4 cm × 3.0–6.0 mm, with conspicuous glands on both sides of the base, margins entire and ciliolate; disc pale-yellow, valvate, 1.5 mm high; corolla white to pale purple outside and vermilion inside, funnel-shaped 4.7–5.3 cm long, outside densely puberulent to puberulous, inside glabrous; tube ca. 3.6–4.5 cm, 4.0–5.0 mm in diameter at base and 12–14 mm in diameter at throat; lobes valvate in bud, erect in open flowers, ovate, 8.0–9.0 × 7.0–8.0 mm, apex emarginate with tip, margins ciliate. Stamens 5, 3.2–3.4 cm long, inserted at base of corolla tube; filaments 2.4–2.5 cm long, flattened at base, lower part connate into a tube, upper part free; anthers 8.0–9.0 mm long, with united spurred at apex, white immature and blue-purple when mature; pistil equal in length to the stamens, stigma and style enclosed by united stamens; stigma club-shaped, 10-ridged, equal in length to the anthers; ovary 2-celled. Fruit berry-like, dark-red, cylindrical, 3.5–4.0 × ca. 5 mm, strigose to strigillose on the surface, bisulcate, calyx lobes persistent. Seeds small, numerous, with pitted testa.

Phenology:— Flowering from October to November and fruiting from November to the following February.

Distribution:— Acranthera burmanica is endemic to Myanmar and known from Kachin State, Putao, where it grows in the understory in tropical rain forests and tropical mountain forests, at an elevation of ca. 900–1500 m.

Discussion:— Acranthera burmanica is morphologically most similar to A. sinensis in the inflorescences borne on short shoots, 1-flowered, leaves on short shoots undeveloped. After comparison with the specimens and literature, we found that A. burmanica can be clearly differentiated from A. sinensis by several characters, as described in the diagnosis above and summarized in Table 1.

Additional specimens examined (paratypes):— MYANMAR. Kachin State: Putao, Shinsan, 97º 53 ʹ 10.48 ʺ E, 27º 41 ʹ 17.60 ʺ. Understory shrubby herbs in tropical mountain forests, alt. 1430 m, 28 Nov. 2014, Myanmar Exped. 188 (HITBC, KUN).

Figures

FIGURE 1. Acranthera burmanica A. Habit. B. Stipule and Flower branch. C. Peduncle. D, F. Bracts. E. Flower bud. G. Inforescences. G. Corolla (adaxial view). I. Calyx. J. Opened corolla. K–L. Stamens. M. Pistil. N–P. Ovary portion. Photographed by Yun-Hong Tan.

FIGURE 2. Acranthera burmanica. A. Habit. B. Stipule and Flower branch. C. Inforescences. D. Infructescence. E. Calyx. F. Opened corolla. G. Stamen. H. Pistil. Illustration by Ling Wang based on the holotype Myanmar Exped. 313.