Shrubs; cystoliths present. Leaves opposite, petiolate; leaf blade margin entire; subisophyllous or anisophyllous. Inflorescences terminal thyrses (the thyrses are branched (then paniculiform) or unbranched (then racemoid); bracts and bracteoles greenish. Calyx unequally five-lobed: posterior lobe largest, two lateral lobes smaller than two anterior lobes. Corolla tube basally cylindrical, expanded distally into a throat; limb two-lipped, upper lip two-lobed, lower lip three-lobed; lobes quincuncial in bud; four stamens, connate to the corolla, not connate to one another, posterior pair shorter than anterior pair, inserted at the base of the corolla throat; anthers bi-thecous; thecae parallel, inserted at different heights, dorsally pubescent, base of each theca spurred; ovary with two ovules per locule; style basally sparsely pubescent; stigma capitate. Capsule stipe absent or barely present; retinacula present. Seeds compressed, brownish, shortly pubescent.

China, Laos, Malaysia, Myanmar, Thailand, Vietnam. Three species in Malaysia.

Lowland dipterocarp forest to upper hill dipterocarp forest.

Chroesthes faizaltahiriana most closely resembles C. longifolia; however, it differs in its inflorescence type, the presence of a terminal raceme not branching (vs. terminal raceme branching) and posterior lobe size ratio 1:4 (vs. 1:2) and corolla length 4.5–5.5 cm (vs. 2–3 cm) and in the corolla tube and lobes being entirely bright yellow to dark orange (vs. entirely dark purple, purplish-red or occasionally white externally) and other significant characters (see Table 1).

Figure 1. 

Chroesthes faizaltahiriana Siti-Munirah A habit of the whole plant B inflorescence (front view) C inflorescence (side view) D flower with bracteoles and calyx E perianth lobes (flower from front view) showing the anthers F calyx and bracteoles G bract H bracteoles I calyx (a) anterior, (l) lateral, (p) posterior lobes (photo of a dry specimen) J corolla (inner view) K corolla (outer view) L stamens. (All photos by Siti-Munirah MY).

Malaysia. Peninsular Malaysia: Kelantan, Gua Musang Distr., Berangkat FR, ca. 822 m alt., 26 Feb 2020, Siti-Munirah, FRI 91215 (holotype KEP!, barcode KEP 280001).

Shrubs 0.7–1 m high. Stems terete, erect, not branched, surface glabrous, diameter ca. 2 mm, swollen at nodes. Leaves opposite; petiole 0.2–1 cm long; straight or twisted (makes the leaf arrangement look decussate); leaf blades elliptic, lanceolate to oblanceolate, 4.5–19 × 1.5–5.5 cm, both surfaces glabrous, lateral veins ca. 8–10 on each side of mid-vein, base attenuate to cuneate, margin entire, apex acute to acuminate. Inflorescence a terminal raceme (unbranched), up to 13 cm long; flowers secund (one bract at each node being sterile, the other bracts subtending each flower), ca. 10-flowered; glandular-pubescent on most parts; peduncles ca. 1 cm; bracts narrowly lanceolate, 20–30 × 2–5 mm, apex acute, glandular-pubescent, conspicuously 1-nerved; bracteoles narrowly lanceolate, 10–15 × 1–2 mm; pedicel short, ca. 1–2 mm long. Calyx 2–3 cm long, posterior lobe lanceolate, 30 × 7 mm, 3–5-nerved, apex acuminate; two anterior lobes, elliptic-lanceolate, 22 × 2–2.5 mm, 1-nerved, apex acuminate; two lateral lobes, linear-lanceolate, 20 × 1 mm, 1-nerved; all glandular-pubescent on both sides; all greenish. Corolla bilabiate, orange-yellow, ca. 4.5–5.5 cm long; outer surface pale yellow, glandular-pubescent; inner surface bright orange-yellow to orange with dark orange spots (or stripes), glabrous; tube with cylindrical basal portion ca. 2 cm long, expanded throat ca. 1.5 cm long; upper lip shortly two-lobed (8–9 mm long), lower lip deeply three-lobed (8–10 mm long). Stamens 4, didynamous, included in the throat, inserted at the base of the inflated part of the corolla, longer pair with filaments ca. 1.5 cm long, shorter pair with filaments ca. 1.2 cm long, all filaments with sparse glandular trichomes on the surface; anther thecae ca. 1–2 mm long, basal spur pointed, surface cover with simple trichomes. Pistil whitish-green; ovary ovoid, 1.5–2 mm long, apex pubescent; style ca. 3.2 cm long, pilose below, glabrous above; stigma subcapitate, minutely bilobed. Fruit not known.

Figure 2. 

Chroesthes faizaltahiriana Siti-Munirah with scale A inflorescence B one floral unit with calyx and bracteole C corolla lobes (All photos by Siti-Munirah MY).

Figure 3. 

Chroesthes faizaltahiriana Siti-Munirah A habit B a flower with bracteoles and calyx front side view C perianth lobes (flower from front view) D bract E bracteole F calyx G corolla (inner view) showing the stamens and pistil H pistil I cross-section of the ovary J stigma K1 anthers front view K2 anthers side view. All from FRI 91215, drawn by Mohamad Aidil Noordin).

Endemic to Peninsular Malaysia, Kelantan. Currently known only from the type collection from Berangkat FR, 5°07'55.5"N, 101°55'28.5"E (Map 1).

Map 1. 

Distribution of Chroesthes faizaltahiriana (▲) and C. lanceolata (■) in Peninsular Malaysia.

Chroesthes faizaltahiriana is found in upper hill dipterocarp forests under shade at 822 m elevation. It was found flowering in February in patches of unlogged forest beside a logging road (Fig. 4).

Figure 4. 

Habitat of Chroesthes faizaltahiriana Siti-Munirah A plant in its original habitat B new logging road beside the population C plant found on the bank of an old logging road (white arrow). (All photos by Siti-Munirah MY).

Chroesthes faizaltahiriana is dedicated to Mohd Faizal Mat Tahir (known as Faizal Tahir), the husband of Siti-Munirah for his strong support in many ways towards the author’s botanical work.

Critically Endangered B2 ab(ii,iii). Following the IUCN Red List Categories and Criteria (IUCN 2019), this species is assessed as critically endangered because it is only known from one locality and AOO is less than 10 km². Furthermore, about eight individuals were observed (all at the flowering stage). The collection locality is within the forest reserve, in an area of disturbed forest near a logging road at an elevation of 822 m. The status of the population is uncertain because the active selective logging activity within the forest reserve is ongoing. It is certainly not within a Totally Protected Area. During the 3-day visit to Berangkat FR, no other populations of C. faizaltahiriana were found. A further survey is needed to obtain more information that could estimate and determine the population size of this species.

Based on the general morphology of this plant, C. faizaltahiriana is close to C. longifolia, which was previously the only known species of Chroesthes in Peninsular Malaysia. However, a detailed comparison has shown that its inflorescence type is entirely different (Fig. 5, Table 1). Additionally, its phytogeography is also different when compared to C. faizaltahiriana, which is endemic to Gunung Berangkat (Kelantan) in upper hill dipterocarp forest (822 m a.s.l.), while C. longifolia is a widely distributed species inhabiting lowland dipterocarp forest. Based on herbarium specimen collections of C. longifolia at Kepong Herbarium (KEP) and the Singapore Herbarium (SING), it has been recorded in Kedah, Perak, Kelantan, Terengganu, Pahang, Selangor, Negeri Sembilan, Melaka and Johor. C. faizaltahiriana is a distinctive species amongst Chroesthes due to its flower colour. It is the only Chroesthes species with bright orange flowers internally. The flowers of C. longifolia are entirely dark purple to deep purplish-red (occasionally white externally), while the flowers of C. lanceolata are white, spotted pink to purple and those of C. bracteata are reported as pale pink, spotted with red.

Figure 5. 

Inflorescence of Chroesthes longifolia from four localities A, A1 Pasoh FR (Negeri Sembilan) B, B1 Tembat FR (Terengganu) C, C1 Nerus FR (Terengganu) D, D1 Gn. Aais FR (Pahang). (Photos: A, A1 Yao TL B, B1 Siti-Munirah MY C, C1 Imin K D, D1 Sam YY).

Shrubs 0.5–3 m tall, anisophyllous. Stems terete, slender, rarely branched, glabrous. Leaves petiole 1–2.5 cm; leaf blade elliptic to oblanceolate to lanceolate, 10–16 × 3–7 cm, both surfaces glabrous, secondary veins 6–9 on each side of mid-vein, base cuneate, margin entire or sub-sinuate, apex acuminate. Inflorescence thyrses 3–7 cm; cymes sessile, 1–3-flowered; peduncles ca.2 cm; bracts elliptic to broadly lanceolate, 3–9 × 1–3 mm, apex acute, glandular-pubescent; bracteoles narrowly elliptic to broadly lanceolate, 4–9 × 0.7–1.2 mm; pedicel 1–5 mm long. Calyx 1–1.6 cm, outside glandular-pubescent; posterior lobe lanceolate, ovate or subelliptic; anterior lobes connate to two-thirds of their length. lateral lobes linear-lanceolate. Corolla white with pink or purple spots, ca. 2.5 cm, outside pubescent; tube basal portion ca. 9 mm, throat ca. 1.5 cm; upper lip two-lobed; lower lip three-lobed. Stamens 4, included in throat; filaments 1–1.2 cm, glabrous; anther thecae 2.1–2.3 mm, pubescent at the apex and along sides, basal spur pointed; ovary apex pubescent; style ca. 2.5 cm. Capsule subellipsoid to obovoid, 1.2–1.6 cm, glabrous or only at apex pubescent, four-seeded. Seeds subcircular in outline.

Myanmar, N Thailand, N Laos, N Vietnam, SW China (Yunnan), Malaysia. In Peninsular Malaysia, recorded from one specimen collected from the trail to Gunung Padang, Ulu Brang, Terengganu in 2010 (FRI 66129) (Map 1).

In Peninsular Malaysia, found in a lowland dipterocarp forest at 473 m a.s.l., under a canopy near a small river. (Trail to Gunung Padang).

Critically Endangered B2 ab(ii). Following the IUCN Red List Categories and Criteria (IUCN 2019), this species is assessed as critically endangered at a national level in Peninsular Malaysia because it is currently known from only one specimen in one locality. It is certainly a very rare species. The forest area is lowland dipterocarp forest which was previously logged in the past and it is not a Totally Protected Area. Globally, its conservation status possibly lists it as least concern (LC), by its wide range distribution.

Terengganu: Hulu Terengganu, Ulu Brang, Ummul-Nazrah et al. FRI 66129 (KEP).

Figure 6. 

Chroesthes lanceolata (T. Anderson) B. Hansen collected from Gunung Padang, Terengganu. (FRI 66129).

Shrub 1–2.5 m high. Stem branches terete, glabrous. Leaves with petiole 0.5–2 cm long; lamina lanceolate, 16–24 × 3.4–8 cm, glabrous, lateral nerves up to 14 pairs, base attenuate, margin entire, apex acuminate. Inflorescence terminal raceme branching, up to 25 cm long; flowers secund, peduncles up to ca. 2.5 cm; one bract at each node being sterile, the other bract subtending one flower; bracts lanceolate, 15–20 × 4.5–6 mm, base obtuse, apex acuminate, glandular-pubescent, nerves conspicuous; bracteoles lanceolate, 10 × 3 mm, as bracts; pedicel very short. Calyx 1.6–1.8 cm long, posterior and anterior lobes elliptic-lanceolate, acuminate, conspicuously nerved, one posterior lobe, elliptic-lanceolate, 18 × 8–9 mm, 3–5 nerved/conspicuously nerved, apex acuminate; two anterior lobes, elliptic-lanceolate, 16 × 5–6 mm, 1-nerved/conspicuously nerved, apex acute; two lateral lobes, linear-lanceolate, 10–12 × 0.5 mm, one-nerved; all glandular-pubescent on both sides; lateral segments linear, one-nerved, glandular-pubescent on both sides; calyx greenish to purplish on the upper part or at the apex. Corolla bilabiate, dark purple-maroon (or claret), 2–3 cm long; outer surface dark purple, dark maroon, claret, sometimes turning white, glandular-pubescent outside; inner surface, dark purple, dark maroon, claret, sometimes whitish on nerves and base, glabrous; narrow part of tube 0.6 cm long, inflated part 1 cm; upper lip shortly emarginate, ca. 3–4 mm long, lower lip deeply trifid, ca. 5 mm long. Stamens 4, inserted at the base of the inflated part of the corolla; longer pair filament 1 cm, shorter pair filament 0.8 cm, filaments 0.8–1 cm long, glabrous, sometimes with glandular trichomes; anthers thecae ca. 1 mm long, glandular-pubescent along the back, bicalcarate at the base. Pistil whitish-green, stigma capitate; ovary glabrous; style ca. 1.4 cm long, pubescent. Capsule ca. 1.5 cm long, glabrous.

Figure 7. 

Chroesthes longifolia (Wight) B. Hansen. The drawing from the original protologue. Source: Icon. Pl. Ind. Orient. 4 (1850) t. 1564.

Malaysia. Endemic to Peninsular Malaysia: Kedah, Perak, Kelantan, Terengganu, Pahang, Selangor, Negeri Sembilan, Melaka and Johor (Map 2).

Map 2. 

Distribution of Chroesthes longifolia (●) in Peninsular Malaysia.

In primary lowland forest up to upper hill dipterocarp forest at 60 to 700 m a.s.l. Sometimes also found in logged and disturbed forests.

Least concern (LC). This is a widespread species throughout Peninsular Malaysia. However, many old collections are from places that have already changed its habitat. Development of these areas has led to population declines. However, its occurrence still has a wide range of distribution and many are still in totally protected areas.

Peninsular Malaysia. Johor: Batu Pahat: 6 November 1892, Lake HW s.n. (SING); Ibid., November 1900, Ridley HN 11127 (SING); Johor Bahru: Sedenak, August 1908, Ridley HN 13496 (SING); Kluang: 16 November 1922, Holttum RE SFN9268 (SING); Kluang FR, 28 August 1950, Sinclair J SFN38950 (SING); Kota Tinggi: Gn. Panti, 23 June 1963, Burkill HM HMB 3178 (SING); Mawai, 9 September 1934, Corner EJH s.n. (SING); Mawai Rd., 24 January 1961, Sinclair J 10563 (SING); Sg. Linggiu, 26 July 1991, Tay EP 91-0052 (SING); Sg. Linggiu, 26 July 1991, Tay EP 91-52 (KEP); Muar: Bkt. Keyara, 1902, Fox W 11283 (SING); Gn. Ledang, June 1892, Ridley HN s.n. (SING); Ibid., Muar, April 1901, Curtis C s.n. (SING); Segamat: Sg. Juasseh, 28 June 1970, Samsuri A SA304 (SING); Kedah: Langkawi, Gn. Machinchang FR, 17 March 1969, Chan YC FRI11209 (SING); Kelantan: Gua Musang, 14 July 1935, Henderson MR SFN29657 (KEP,SING); Gua Musang: Relai FR, 1 September 1992, Hamid H2 (KEP); Kuala Krai: Gn. Stong, 5 March 1924, Mhd Nur SFN12180 (SING); Stong FR, 31 March 2009, Rosdi M FRI66253 (KEP SING); Stong Tengah FR, 6 February 2007, Chew MY FRI53481 (KEP); Kuala Lumpur, February 1890, Curtis C 2362 (SING); Melaka: Jasin: Air Panas, 5 September 1886, Watchman under Derry 667 (SING); Air Panas, November 1893, Goodenough JS 1690 (SING); Chabau, 22 September 1885, Alvins MV 2256 (SING); Merlimau, June 1889, Derry R 221 (SING); Negeri Sembilan: Jelebu: Pasoh FR, 3 June 1987, LaFrankie JV LJV2276 (KEP); Ibid., 4 July 1982 Kiew R RK1186 (KEP); Ibid., 30 August 2010, Yao TL FRI65469 (KEP); Kuala Pilah: Angsi FR, Gn. Angsi, 10 December 1930, Syed A FMS23764 (KEP, SING); Senaling, 24 June 1930, Corner EJH s.n. (SING); Senaling Inas,18 November 1929, Symington CF FMS 21356 (KEP, SING); Senaling Inas FR, 28 November 1922, Holttum RE 9788 (SING); Rembau: Perhentian Tinggi, December 1898, Ridley HN s.n. (SING); Pahang: Bentong: Clough FR, Cpt. 37, 16 July 1958, Kochummen KM KEP78709 (KEP); Bentung, Karak FR, 14 July 1924, Best, GA, SFN13899 (SING); Jerantut: Gn. Aais FR, 5 July 2004, Sam YY FRI49062 (KEP); Ibid., 6 July 2004, Chua LSL FRI46691 (KEP); Kota Gelanggi, August 1891, Ridley HN 2174 (SING); P. Tawar, July 1891, Ridley HN s.n. (SING); Taman Negara Gn. Tahan, 31 July 1996, Kiew R RK3978 (KEP); Taman Negara, Sg. Riul, 12 July 1970, Everett B FRI14436 (KEP); Taman Negara Ulu Sat Tg. Petir, 12 July 1970, Whitmore TC FRI15267 (KEP); Taman Negara Kuala Keniam, 7 September 2020, Siti Munirah MY FRI94881 (KEP); Lipis: Chegar Perah,14 October 1927, Henderson MR SFN19364 (SING); Maran: Jengka FR, 10 April 2001, Sam YY FRI 46518 (KEP); Temerloh: Gn. Benom, 14 June 1968, Teo LE 2714 (SING); Temerluh: Fort Iskandar, 2 March 1950, Woods MC KL1720 (SING); Ibid., 2 March 1959, Woods MC KL1720 (KEP); Gn. Senyum, 30 July 1928, Henderson MR s.n. (SING); Kemasul FR, 16 September 2006, Hamid FMS10598 (KEP); Krau WR, 10 November 1999, Damahuri S FRI45314 (KEP); Krau WR 12 July 2007, Mohd Hairul MA FRI58921 (KEP); Perak: Hulu Perak: Belum FR, 30 December 1993, Davison GWH UPM 6077 (KEP); Selangor: Gombak: Bkt. Lagong FR, 5 May 1976, Chan YC FRI23956 (KEP, SING); Ibid., 11 November 1959, Kochummen KM KEP94047 (KEP, SING); Kanching FR, 17 September 1925, Strugnell EJ FMS10508 (KEP); Kepong, 27 May 1970, Teo LE 2862 (SING); Ulu Gombak, 4 July 1918, Sanger-Davies AE FMS2376 (KEP, SING); Hulu Langat: Bkt. Batu Balai, 1 August 1959, Gadoh U KL1630 (KEP); Bkt. Enggang, 3 April 1930, Symington CF FMS 24134 (SING); Bkt. Tangkol, 1 October 1959, Gadoh U KL1810 (KEP); Bkt. Tangkol, 25 July 1959 Gadoh U KL1621 (KEP); Ulu Langat, 7 June 1979, Rajoo SA237 (KEP); Hulu Selangor: Gading Forest Reserve, 19 July 1969, Chan YC FRI11235 (KEP); Klang, Klang Water Catchment Forest, 12 March 1922, Burkill IH SFN6849 (SING); Petaling: Air Hitam Forest Reserve, 12 September 1985, Kiew R RK2065 (KEP); Petaling Rd., 21 June 1889, Ridley HN s.n. (SING); Sungai Buloh Forest Reserve, 7 October 1926, Strugnell EJ 12495 (KEP); Sungai Buloh Forest Reserve, 13 August 1923, Hamid FMS 8888 (KEP); Labu River, Ridley HN s.n. (SING); Sungai Buloh, 12 December 1923, Mhd Nur SFN11886 (SING); Sungai Buloh, 23 November 1956, Burkill HM HMB (SING); Terengganu: Dungun: Bukit Bauk, 25 January 1994, Kiew R RK3793 (KEP); Hulu Terengganu: Sg. Petuang, 26 March 1974, Ng FSP FRI22026 (KEP); Tasik Kenyir, 3 August 2007, Kamarul Hisham M FRI52138 (KEP, SING); Tasik Kenyir, 3 August 2007 Julius A FRI56144 (KEP); Tembat Forest Rerserve, 6 April 2009, Rosdi M FRI66281 (KEP); Tembat Forest Reserve, 3 April 2009, Siti Munirah MY FRI67889 (KEP); Setiu: Ulu Setiu Forest Reserve, 7 March 2002, Saw LG FRI44390 (KEP); Nerus Forest Reserve, Gunung Sarut, 24 June 2019, Imin K FRI 94046 (KEP).

Ridley (1923) mentioned Chroesthes macrantha as present in Peninsular Malaysia based on Wray 3385 from Perak and that it is similar to C. longifolia. Hansen (1983) suggested that C. macrantha was probably a form of C. longifolia, but he had not observed Wray 3385, so was not able to clarify its status. Efforts to search for this specimen have also been unsuccessful. To date, the status of this taxon is uncertain. Besides, this name also appears not to have been validly published.

Figure 8. 

Chroesthes longifolia (Wight) B. Hansen, collected from Taman Negara, Pahang (Kuala Keniam) A habit B–D inflorescence B front view C side view D back view E bract F–I flower with bracteoles and calyx F from the top view G lower view H–I side view J corolla (inner view) showing the stamens and pistil K corolla lips (flower from front view) showing anthers (All photos by Siti-Munirah MY).