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

Fig. 2

Type.

China – Guizhou Prov. • Jiangkou County, Fanjing Mountain , along the hiking trail in forests; 27 ° 53 ' 45.08 ″ N, 108 ° 42 ' 39.09 ″ E; alt. 1635 m; 1 Sep 2018; Y. P. Chen et al. EM 590 (holotype: KUN 1628213 !; isotypes: K!, KUN 1628215 !, PE!) .

Diagnosis.

Isodon attenuatus is most closely related to I. villosus , but differs by having subglabrous (vs. densely to sparsely villose) laminae with a decurrent (vs. not decurrent) base, densely puberulent and glandular puberulent (vs. densely villose and glandular puberulent) inflorescences, longer pedicels (4–6 mm vs. 2.5–4 mm long), triangular (vs. ovate) calyx teeth and a corolla tube attenuate towards the throat (vs. not attenuate).

Herbs perennial, 30–70 cm tall. Rhizomes woody, tuberose. Stems erect, branched, quadrangular, densely puberulent and reddish-brown glandular. Leaves decussate; lamina ovate to broadly ovate, papery, 5–15 × 3–7 cm, apex acuminate, base cuneate to broadly cuneate, margin crenulate, adaxially green, subglabrous to sparsely pubescent, reddish-brown glandular, abaxially light green, subglabrous, densely reddish-brown glandular; lateral veins 3–5 - paired; petioles 1–5 cm long. Thyrses terminal and axillary, ca. 10 cm long; cymes 3–7 - flowered, peduncles 2–3 mm long, pedicels 4–6 mm long, densely puberulent, glandular puberulent and reddish-brown glandular; bracts broadly ovate, sessile, apex lanceolate, margin entire, 3–10 mm long, bracteoles linear, ca. 1 mm long, ciliate, densely reddish-brown glandular. Calyx campanulate, ca. 2 mm long, densely glandular puberulent and reddish-brown glandular outside; 2 - lipped to 1 / 2 its length, teeth triangular, apex acute, fruiting calyx dilated to ca. 5 mm long. Corolla 5–6 mm long, declinate, pubescent and reddish-brown glandular outside; tube 3–3.5 mm long, white, saccate abaxially near base, ca. 2 mm in diameter, attenuating gradually towards throat to ca. 1 mm in diameter; apex 2 - lipped, light bluish-purple, posterior lip 4 - lobed, ca. 3.5 × 3.5 mm, reflexed, lobes oblong, apex acute, anterior lip entire, subrounded, concave, straight, 2–3.5 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, ochre-yellow, oblong, 1.4–1.55 mm long, ca. 1 mm wide, smooth and glabrous.

Phenology.

Flowering from July to September, fruiting from August to October.

Distribution and habitat.

Currently, I. attenuatus is only known from the Fanjing Mountain in Guizhou Province, China (Fig. 1 ). The new species usually grows in evergreen broadleaf forests at altitudes of 1600–2000 m.

Etymology.

The specific epithet refers to the gradually attenuating corolla tube of the new species towards the throat.

Chinese name (assigned here).

jiàn xiá xiāng chá cài (渐狭香茶菜).

Additional specimens examined.

China – Guizhou Prov. • Jiangkou County, vicinity of Jinding along the crest of the Fanjing Shan Mountain Range ; alt. 2000–2300 m; 28–29 Aug 1986; Sino-American Guizhou Botanical Expedition 673 ( L 3902407 !, PE 00833681 !) ; • ibid.; alt. 1707 m; 20 Oct 2017; Y. P. Chen & L. Chen EM 429 ( KUN!) .

Figures

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

Figure 2. Morphology of Isodon attenuatus from the type locality A habitat B, C habit D abaxial view of lamina E, F inflorescences G infructescence H flowers I corollas J dissected corolla K calyces L ovary M style N mericarps (Photographed by Ya-Ping Chen).