Perilimnastes fruticosa (Ridl.) Ridl., J. Straits Branch Roy. Asiat. Soc. 79: 70, in obs. 1918; Ridley, Fl. Mal. Penins. 1: 773. 1922.

Erect shrubs, erect/ascending shrublets or caulescent herbs, sometimes with raphides in many parts. Stems terete, obtusely 4-sided or ribbed, with uniseriate or multiseriate, appressed or spreading hairs, rarely glabrous. Leaves opposite, equal, subequal or unequal in a pair, petiolate, rarely sessile (in P. sessilifolia); leaf blades elliptic, ovate, elliptic-lanceolate, obovate, oblanceolate or suborbicular, submembranous, papery or stiffly papery, 3–7-nerved, base cuneate, acute, rounded, subcordate to broadly cordate, margin entire or inconspicuously serrulate or denticulate. Inflorescences usually terminal (rarely axillary) umbels subtended by two or more bracts, many- to few-flowered, sometimes reduced to a single flower. Flowers 4-merous; hypanthia ± campanulate, cup-shaped or funnel-shaped; calyx lobes triangular, ± attenuate to ligulate or linear; petals white, pink or purplish, obovate, ovate, oblong, or elliptic, more or less oblique, apex acute or acuminate; stamens 8, equal or subequal; anthers isomorphic, yellow, pinkish or purplish, narrowly ovate to lanceolate, curved to ventral side, connectives ventrally inappendiculate and dorsally spurred, or basally forming a collar with two ventral auricles/lobes/ridges and a dorsal spur; ovary half inferior, ovoid, 4-celled, crown of four partly or fully connate lobes; style filiform. Old capsule cup-shaped, campanulate, quadrangular, crown persistent and enlarged, enclosing an obpyramidal space; placental column 4-horned; placentas thready. Seeds numerous, minute, cuneate. (Figs 2–4)

Twenty species and two varieties, eight species (seven endemic) and two varieties in southernmost China (Guangdong, Guangxi, Hainan, Yunnan), eight (seven endemic) in Vietnam, one on the Malay Peninsula and four in Borneo (Fig. 5).

Vietnam. Đà Nẵng: Hòa Ninh, Ba Na Hills, 1,360 m elevation, in forests on damp slopes near steam, 22 Nov 2019, Jin-hong Dai and Ying Liu 813 (holotype: PE; isotypes: A, SYS, VNMN).

When publishing A. fruticosus, Ridley (1908) designated L.Wray and H.C.Robinson 5453 as the type without citing a particular herbarium, only stating that the whole collection made by Robinson’s expedition should be sent to the British Museum (BM). Nayar revised Perilimnastes in 1974 and noted the specimen in BM as holotype of this species. This was probably only a speculation rather than deliberate lectotypification. In the revision of Phyllagathis, Cellinese (2002) chose a duplicate sheet in K as the lectotype, but did not include the phrase “designated here” in the typification statement, as required by Art. 7.11 of the Code (Turland et al. 2018). The specimen sheet in BM [BM000565932] is here designated as the lectotype to eliminate any uncertainty.

Vietnam. Quảng Nam Province: Đại Lộc, about 400 m south of Khu Du Lich Sinh Thai Khe Lim, along newly opened road, 574 m elevation, on rocks along a stream, 23 Nov 2019, Jin-hong Dai and Ying Liu 821 (holotype: PE; isotypes: A, SYS, VNMN).

Phyllagathis calisaurea was described, based on specimens collected in western Guangxi, China (Chen 1984b). Subsequent authors did not recognise it as a distinct species and synonymised it within P. ovalifolia (Hansen 1992; Chen and Renner 2007). Phyllagathis calisaurea and P. ovalifolia have adjacent distribution ranges (Guangxi vs. Yunnan, China). They are morphologically quite similar, with the only differences being leaf size (6.5–11.5 × 2–3.7 cm vs. 9–18 × 3–8.5 cm), leaf shape (ovate lanceolate vs. ovate to elliptic) and indumentum of the stems and leaves. Nonetheless, they failed to form a monophyletic group in both the previous (Zhou et al. 2022) and current phylogenetic analyses (Fig. 1). As only one accession of P. ovalifolia was included in these analyses, the boundary between P. ovalifolia and P. calisaurea needs to be further investigated using multiple accessions from across the distribution range. For the time being, we adhere to the species delimitation proposed by Hansen (1992) and Chen and Renner (2007).

Malaysia. Sarawak: Mt Dulit, Ulu Koyan, alt. 800 m, 16 Sept 1932, S.Synge 503 (holotype: K! [K000867704]).

Vietnam. Lâm Đồng Province: Đà Lạt, Bidoup Nui Ba National Park, 1,500–1,700 m elevation, at damp places under forest, 29 Nov 2019, Jin-hong Dai and Ying Liu 836 (holotype: PE; isotypes: A, SYS, VNMN).

Vietnam. Đà Nẵng: Hòa Ninh, Ba Na Hills, 1,360 m elevation, in forests on damp rocks along steam, 22 Nov 2019, Jin-hong Dai and Ying Liu 814 (holotype: PE; isotypes: A, SYS, VNMN).

China. Guangdong Province: Taishan County, Chixi Town, near Zhuxing Village, 200–300 m elevation, amongst rocks along a stream in forests, 15 Jun 2022, Chun-yu Zou 3608 (holotype: IBK; isotypes: IBK, PE).

Resembles P. stenophylla in leaf morphology, but differs in height (to 0.15 m vs. 0.8 m tall), number of flowers per inflorescence (1 vs. 2–3-flowered), length of the peduncle (10–22 mm vs. 4 mm) and the shape of calyx lobes (broadly obovate vs. narrowly triangular). Resembles P. setotheca in having 4-sided branchlets, large and persistent bracts below flower and stamen morphology, but differs in plant size (to 0.15 m vs. 1 m tall), leaf shape and size (oblong-lanceolate or obovate-lanceolate, 1.7–7 × 0.73–2.2 cm vs. oblong-lanceolate, elliptic or obovate, 10–20 × 3–8 cm) and number of flowers per inflorescence (1-flowered vs. 3 to more than 20-flowered).

Dwarf shrubs, much-branched, ascending, to 0.15 m tall, with druses in many parts. Stems and leaves sparsely puberulent with minute brown hairs (with few-celled stalk and a glandular head) when young, glabrous when mature. Stems obtusely 4-sided; branchlets 4-sided, with four ribs and two additional ridges extending from the base of the leaf petioles. Leaves opposite, equal to subequal in a pair, glabrous when mature; petiole 2–22 mm; leaf blade oblong-lanceolate or obovate-lanceolate, 1.7–7 × 0.73–2.2 cm, thick papery, 3-veined, green to dark green adaxially, pale green abaxially, base cuneate, apex acute, margin basally entire and remotely denticulate to repand above the base or the middle. Inflorescences terminal, peduncles 1–2.2 cm long; flower solitary, subtended by one or two pairs of leaf-like bracts, bracts 1–1.8 × 0.7–0.9 cm, persistent in fruit. Flowers 4-merous; pedicel 4-sided, ca. 4 mm long in flower and 4–10 mm in fruit; hypanthia funnel-shaped, glabrous, ca. 7 × 6 mm; calyx lobes 4, broadly obovate, glabrous, 4–5 × 5 mm; petals pinkish-purple, ca. 15 × 7 mm, obovate, oblique, apex acute or short acuminate, glabrous on both sides; stamens 8, isomorphic, filaments 8–10 mm long, white or pink, glabrous, anthers ovate-lanceolate, curved to ventral side, pinkish-purple with yellow base, ca. 9 mm long, connective dorsally forming a 0.7–1 mm long spur and ventrally forming two yellow ridges; ovary ca. 3 mm long, half as long as hypanthium (crown excluded), ovary crown wedge-like, 4-lobed; styles 20 mm long. Old (post-mature) capsules cup-shaped, 7–9 × 4–7 mm, 4-sided; hypanthium 8-ribbed; crown enlarged and enclosing an obpyramidal space; placental column unbeaked, 4-horned; placenta thready.

Flowers in May and June, old capsules in October.

The specific epithet is based on the habit of this species, viz. dwarf shrubs to 15 cm tall.

Perilimnastes nana is currently known from Taishan County, Guangdong Province, China (Fig. 8). It grows amongst rocks along streams in the forest, at 200–300 m elevation.

During a survey of herbarium specimens of Phyllagathis in IBSC, a collection (Ze-xian Li et al. 516) from Taishan, Guangdong, China caught our attention. This plant (P. nana) closely resembles P. stenophylla from Hainan Island in the oblong-lanceolate leaf blades and was misidentified as the latter species. Closer inspection reveals that it has strictly 1-flowered inflorescences and broadly obovate calyx lobes, which distinguishes it from P. stenophylla. Field trips in 2022 and 2023 revealed other differences between the two species, such as plant size and peduncle length. Perilimnastes nana is phylogenetically closest to P. setotheca, a species found in Guangdong, Guangxi and Hainan China (Fig. 8). However, they differ markedly in plant size, leaf shape and size and number of flowers per inflorescence. As a result, P. nana is quite distinct from its closest relatives, prompting us to describe it as a new species.

China. Guangdong Province: Taishan County, Chixi Town, Zhuxing Village, 220 m elevation, 17 Oct 2023, Ying Liu 892 (SYS); Taishan County, Chixi Town, Liugushan, 8 May 1981, Ze-xian Li et al. 516 [IBSC (IBSC0223903)].