Dimetia brevipetiolata R. J. Wang, 2020

Zhang, Ying, Jiang, Guo-Bin & Wang, Rui-Jiang, 2020, Dimetia brevipetiolata (Spermacoceae: Rubiaceae): A new species from Guangxi, China, Phytotaxa 428 (1), pp. 43-50 : 45-46

Dimetia brevipetiolata R. J. Wang , sp. nov., 短ijkª4 Figs. 1 & 2 .

Type: CHINA. Guangxi Zhuang Autonomous Region, Rong county, Shizhai Town , Duqiaoshan Scenic Area , riverside, long-styled flowers, 22º47’37.5” N, 110º36’18.4” E, ca. 100 m a.s.l., 02 April 2013, Rui-Jiang Wang & Shu-Jun Deng 2304 (holotype: IBSC0847225 ; isotypes: IBSC) .

Dimetia brevipetiolata is similar to D. scandens with respect to its terete stem, lanceolate and thick papery leaves, indistinct secondary veins and compound-cymose inflorescences, but differs in the prostrate and herbal habit (vs. scandent and woody), subsessile leaf (vs. subsessile-5.0 mm long petioled), rounded leaf base (vs. acute to cuneate), nearly glabrous corolla (vs. densely villous adaxially) and indehiscent capsules (vs. dehiscent) ( Table 2).

Description

Semi-prostrate herbs, 20–30 cm tall, glabrous. Stems terete, up to 3 mm in diameter, pubescent at young branches but glabrous with growing. Leaves opposite, subsessile; blade thick papery, glabrous, lanceolate or narrowly elliptic, apex acute or shortly acuminate, base rounded, 1.8–5.0 × 1.0– 2.5 cm; midrib depressed and pubescent adaxially, prominent and glabrous abaxially; secondary veins usually in 3 (–4) pairs, indistinct on both sides. Stipules interpetiolar, fused to petiole bases, triangular, apex acute, 1.2–1.3 × 0.2–0.4 mm. Inflorescence terminal, compound cyme; peduncles sparsely pubescent, 0.5–2 cm long, terete; bracts lanceolate, 0.5–1.8 × 0.2–0.5 mm; bractlets triangular, 0.4–0.9 × 0.1–0.3 mm. Flowers heterostylous; pedicels pubescent, subsessile or up to 3 mm long. Calyx sparsely pubescent abaxially, hypanthium obconic, 0.8–1.2 mm long; lobes 4, triangular, apex acute, 0.7–1.3 × 0.5–1 mm. Corolla white, tube 2.1–3.0 mm long, sparsely pubescent at throat; lobes 4, oblong-lanceolate, 1.1–2.7 × 0.8–1.5 mm. Stamens 4, anthers oblong-linear, ca. 0.6 mm long. Stigma bilobed, papillate, 0.5–0.9 mm long. Long-styled flowers: styles exserted, 3.5–4.5 mm long; stamens included, adnate to the middle of corolla tube; filaments short, ca. 0.2 mm long. Short-styled flowers: styles included, 1.4–2.0 mm long; stamens exserted, adnate to the throat of corolla tube; filaments ca. 2.3 mm long. Capsules ellipsoid to subglobose, or ovoid, 2.0–2.5 × 1.5–2.0 mm, glabrous, with persistent calyx limbs, protruded and indehiscent at apex. Seed numerous, minute, ca. 0.3 mm, deep brown, with angled and reticulate surface.

Phenology: Flowering occurs in March–April, fruiting in May–July.

Figures

FIGURE 1. Dimetia brevipetiolata R. J. Wang, sp. nov. A: Habit, B: Branchlet, C: Inflorescence, D: Long-styled flower, E: short-styled flower, F: Leaf blade, G: Stipule shape, H: Infructescence, I: Capsule, J: Seeds (Photos by Rui-Jiang Wang & Guo-Bin Jiang).

FIGURE 2. Micromorphology of Dimetia brevipetiolata R. J. Wang, sp. nov. A–C: Pollen morphology of long-styled flowers (from Rui-Jiang Wang & Shu-Jun Deng 2304, IBSC), D–F: Pollen morphology of short-styled flowers (from Rui-Jiang Wang & Shu-Jun Deng 2305, IBSC).