Isodon sukungii Y. P. Chen & C. L. Xiang, 2024

Chen, Ya-Ping, Peng, Hua, Paton, Alan J. & Xiang, Chun-Lei, 2024, Three new species of Isodon (Nepetoideae, Lamiaceae) from China, PhytoKeys 246, pp. 283-293 : 283-293

Isodon sukungii Y. P. Chen & C. L. Xiang sp. nov.

Fig. 4

Type.

China – Sichuan Prov. • Muli County, Sanjiaoya Town, on the way from Biji to Guoquanyan , amongst the thickets on the dry valley slope; 28 ° 04 ' 58.50 ″ N, 101 ° 28 ' 8.77 ″ E; alt. 2041 m; 13 Oct 2018; Y. P. Chen et al. EM 666 (holotype: KUN 1628218 !; isotypes: K!, KUN 1628217 !, PE!) .

Diagnosis.

Isodon sukungii is morphologically similar to I. tenuifolius but differs by having longer laminae (1–4 cm vs. 0.5–1 cm long) with serrate (vs. entire) margins, cymes that form panicles (vs. single cymes that do not form thyrses or panicles) and a longer corolla (6–7 mm vs. 4 mm long) with a straight (vs. strongly reflexed) anterior lip.

Shrubs 30–120 cm tall. Stems erect, much branched; branches brown, decorticate, subterete, glabrescent; branchlets brown, obtusely 4 - angled, densely grey tomentose. Leaves decussate; lamina ovate to oblong, thick papery, 1–4 × 0.5–2 cm, apex acute, base cuneate to subrounded, margin serrate, rarely entire, adaxially green, sparsely minute grey tomentose and glandular, abaxially white, densely grey tomentose and glandular, lateral veins 3–5 - paired, conspicuously elevated abaxially; petioles 0.3–1 cm long, densely grey tomentose. Cymes 3–7 - flowered, often forming secund panicles up to 20 cm long; bracts leaf-like, gradually reduced towards apex, margin entire, longer than cymes, upper ones sessile, lanceolate, bracteoles linear, ca. 1 mm long; peduncles 1–3 (– 5) mm long, pedicels 1–2 mm long, densely grey tomentose. Calyx campanulate, 2.5–3 mm long, densely grey tomentose and glandular outside, slightly 2 - lipped to 1 / 3 its length; teeth subequal, ovate-triangular, apex acute, fruiting calyx slightly dilated to ca. 4 mm long. Corolla white, 6–7 mm long, declinate, pubescent and glandular outside; tube 3.5–4 mm long, saccate abaxially near base, ca. 1.5 mm in diameter; apex 2 - lipped, posterior lip 4 - lobed, dotted with reddish-purple spots, ca. 2.5 mm long, reflexed, lobes subrounded, anterior lip entire, subrounded, concave, navicular, straight, 2.5–3 mm in diameter. Stamens 4, included; anther cells 2, confluent, divergent; filaments pubescent at base. Style included, glabrous, apex slightly subequally 2 - lobed. Mericarps 4, brown, oblong, 1.25–1.35 mm long, 0.85–0.95 mm wide, smooth and glabrous.

Phenology.

Flowering from July to November, fruiting from September to December.

Distribution and habitat.

Isodon sukungii is widely distributed in the dry valley along Min River, a tributary of the Yangtze River, in Sichuan Province, southwest China (Fig. 1 ). The new species usually grows on open dry slopes with savannah-like vegetation at altitudes of 1600–2700 m.

Etymology.

The new species is named after the late Prof. Su-Kung Wu, who is one of the earliest Chinese botanists to explore the plant diversity of Muli County.

Chinese name (assigned here).

sù gōng xiāng chá cài (素功香茶菜).

Additional specimens examined.

China – Sichuan Prov. • Muli County, on the way from Moshuogou to Boao ; alt. 1900–2290 m; 6 Sep 1959; S. K. Wu 2419 ( KUN 0271016 !, KUN 0271017 !) ; • Muli County, Boao, Baidiao ; alt. 2150 m; 20 Sep 1959; S. K. Wu 3155 ( KUN 0271018 !, KUN 0271019 !) ; • Muli County, Housuo Town, Xiagu Village ; 26 Jul 2011; E. D. Liu et al. 2911 ( KUN 1278979 !) ; • Muli County, Kala Town, Tianzheng Village ; alt. 1966 m; 15 Oct 2018; Y. P. Chen et al. EM 689 ( KUN!) ; • Yanyuan County, Ma’anshan Town, Songlinping Village ; alt. 1663 m; 15 Oct 2017; Y. P. Chen & Z. H. Wang EM 419 ( KUN!) ; • Yanyuan County, Jinhe Town ; 4 Oct 2020; L. B. Jia s. n. ( KUN!) ; • Yajiang County ; alt. 2570 m; 18 Aug 2011; W. Fang et al. FW 11269 ( KUN 1340269 !, KUN 1340270 !) ; • ibid.; alt. 2711 m; 28 Aug 2020; Y. P. Chen et al. EM 1711 ( KUN!) .

Figures

Figure 1. Geographic distribution of Isodon attenuatus (red triangle), I. gongshanensis (green circles) and I. sukungii (purple squares).

Figure 4. Morphology of Isodon sukungii from the type locality A habitat B, C habit D, E inflorescences F infructescence G leaves H flowers I corollas J dissected corolla K dissected calyces L pistil M mericarps (Photographed by Ya-Ping Chen).