Pogostemon fraternus Miquel 1856

13. Pogostemon fraternus Miquel (1856: 963). Lectotype (designated by Keng 1969: 159):— INDONESIA. West Java: op den G. Praoe, no date, T. Horsfield 1141 (K).

Annual herb, 20–70 cm tall. Stems solid, terete, procumbent or diffuse and rooting sometimes at base, hairy upward. Leaves opposite; petiole 1–4.5 cm long, subglabrous; blade ovate to ovate-lanceolate, 2.5–9 × 1–5 cm, membranous or papery, subglabrous, base cuneate or rounded, margin serrate to double serrate, apex acute or acuminate, lateral veins 3–6 pairs on each side of the midvein. Spike terminal, unbranched or sometimes with more than two lateral branches, 5–15 × 1.2–1.5 cm, loose; peduncle 0.5–2.5 cm long; verticillasters 5–11-flowered, flowers with a pedicel 2.5–4 mm long. Bracts and bracteoles linear, 2–4 mm long, hairy. Calyx subtubular, 4–6 mm long, 2-lipped, 10-veined, sparsely hairy and glandular outside, an annulus of hairs in the throat; teeth 5, margin minutely hispid, postieror 3 narrowly triangular, ca. 1.5 mm long, anterior 2 subulate, ca. 2 mm long. Corolla purplish or pink-purple, to 7.5 mm long, 4-lobed, subequal. Stamens 4, violet, filaments inserted at different heights, the lowest at a hight of 3.5 mm in the tube; filaments 8.0– 8.8 mm long, exserted portion ca. 4.8 mm; filaments more or less glabrous towards the base; anthers 1-locular, cell apex dehiscent; style ca. 11 mm long, violet; stigma bifid, equal, lobes 0.6–0.9 mm. Disc ca. 0.8 mm long. Nutlets 4, ca. 1.1 × 0.9 mm, subglobose, abaxially flattened, adaxially ribbed, reticulate-foveate.

Distribution and habitat:— The species is widespread from north India to China, Thailand, Myanmar, Vietnam, and Java. In China, it is only found in south Yunnan (Figure 10). It grows in streamsides or wet areas in forests, at an elevation of 1000–1400 m.

Phenology:— Flowering from March to April.

Taxonomic notes:— Keng (1969) erroneously reduced Pogostemon fraternus to the synonymy of P. menthoides Blume (1826: 825). This treatment was wrongly followed in many previous Chinese publications (Wu & Huang 1977, Wu et al. 1977, Wu et al. 1984, Li & Hedge 1997). However, Pogostemon fraternus can be easily distinguished from P. menthoides by the stem being subglabrous (not pubescent), the leaves 2.5–9 × 1–5 cm (not 3–5.5 × 1.5–4 cm), with cuneate to rounded (not cuneate) base and a petiole to 5 cm long (not less than 2 cm long), the calyx of flowers 4–6 mm long (not ca. 3.5 mm long), and the corolla to 7.5 mm long (not ca. 4.5 mm long). All Chinese specimens examined are idenfical with P. fraternus, and P. menthoides is obviously not found in China.

Bhatti & Ingrouille (1997) errenuously considered Horsfield 29 as the type of P. menthoides. However, the syntypes of P. menthoides were collected by Korthals and Blume, and Blume s.n. was designated by Keng (1969) as the lectotype.