Calanthe rubens Ridl.

Kurzweil, Hubert, 2010, A precursory study of the Calanthe group (Orchidaceae) in Thailand, Adansonia (3) 32 (1), pp. 57-107 : 65-66

2. Calanthe rubens Ridl.

( Fig. 2 )

Gardeners’ Chronicle, III, 1890: 576 (1890); Seidenfaden & Smitinand, The Orchids of Thailand – A Preliminary List, part III: 333 (1961); Seidenfaden & Smitinand, The Orchids of Thailand – A Preliminary List, part IV, 2: 792 (1965); Seidenfaden, Dansk Botanisk Arkiv 29: 30 (1975); Seidenfaden, Opera Botanica 114: 89 (1992); Seidenfaden & Wood, The Orchids of Peninsular Malaysia and Singapore: 165 (1992). — Alismorkis rubens (Ridl.) Kuntze, Revisio Generum Plantarum 2: 650 (1891). — Preptanthe rubens (Ridl.) Ridl. , Flora of the Malay Peninsula 4: 123 (1924). — Types: Peninsular Malaysia, Langkawi, date illegible, Curtis 218 (syn-, SING!); Peninsular Malaysia, Langkawi, 3.I.1890, Curtis s.n. (syn-, SING!).

ADDITIONAL MATERIAL EXAMINED. — Eastern, Nakhon Ratchasima, Kao Sisiat, 18.I.1925, Kerr 0214 ( BK, C, K). — Eastern , Si Sa Ket, Seidenfaden & Smitinand 8137 (C spirit). — Central , Saraburi, Menam Pasak Kengkoi , 9.XII.1923, Kerr 0122 (C, K). — Central , Saraburi, XII. 1963, Cumberlege 506 (K spirit). — South-Eastern , Prachin Buri, Songkakul 80 ( BKF spirit). — South-Eastern , Rayong, Khao Cha Mao , Shimizu et al. 23473 (C spirit). — South-Eastern , Chanthaburi, Kao Subap , 7.I.1930, Kerr 0785 ( BK, C, K, L). — South-Eastern , Chanthaburi, Seidenfaden & Smitinand 5884 (C spirit). — Peninsular , Surat Thani, Ban Tham Pueng , 21.II.2006, Suksathan 3817-1 ( QBG, QBG spirit). — Peninsular , Surat Thani, Ko Samui , 25.I.1929, Kerr s.n. (K). — Peninsular , Surat Thani, 22.II.1930, Kerr 0790 ( BK, K). — Peninsular , Phangnga, Ko Chong Lat , Seidenfaden & Smitinand 6487 (C spirit). — Peninsular , Phangnga, 28.XI.1929, Kerr 0720 ( BK, C, K); Kerr s.n. ( BK SN243536); 27.II.1929, Kerr s.n. (K). — Peninsular, Krabi, Kow-Pra Bahng Krahm Wildlife Sanctuary, 18.I.2006, Maxwell 06-76 ( CMU [Sc], CMU [Sc] spirit). — Peninsular, Krabi, Ban Khao Thong, 20.I.1966, Seidenfaden & Smitinand 6260 (C spirit). — Peninsular, Nakhon Si Thammarat, Tung Song, 13.II.1928, Put 2361 ( BK, C, K). — Peninsular, Trang, 29.XI.1985, Kurzweil 706 (K). — Peninsular, Satun, Adang, 12.I.1928, Kerr 0486 ( BK, C, K, L). — Peninsular, Satun, Tang Wa, 6.I.1928, Kerr s.n. (K H2006/01478-255). — Peninsular, Satun, Ko Terutao, Seidenfaden & Smitinand 6549 (C spirit). — Peninsular, Satun, Taleban National Park , 21.I.85, Seidenfaden & Smitinand 9363 (C spirit). — Peninsular, Satun, Way s.n. (C L69/2006-40). — Peninsular, Pulau Kopang, 28.XI.1918, Haniff & Low 3564 ( SING). — Peninsular, Selim, I. 1923, Put sub Smith 001 (K). — Without locality, Menzies & DuPuy 53 (K spirit); 7.I.1988, Nanakorn et al. 10440 ( QBG spirit); Niyomdham 2135 ( BKF spirit); Thaithong 798 ( BCU spirit) .

ILLUSTRATIONS. — Seidenfaden & Smitinand, The Orchids of Thailand – A Preliminary List, part III: fig. 253 (1961); Seidenfaden, Dansk Botanisk Arkiv 29: fig. 10a-c, pl. V (1975); Seidenfaden & Wood, The Orchids of Peninsular Malaysia and Singapore: fig. 71c, pl. 9b (1992).

DESCRIPTION

Terrestrial or lithophytic herbs, deciduous, 25- 75(-132) cm tall. Basal sheaths not seen.Pseudobulbs prominent, ovoid, conical, 2.5-12 × 2.5-3.5 cm, close together, several-noded with the largest part made up of a single internode, covered by greyishsilvery leaf sheaths, glabrous. Leaves 1-3, annual and usually not present at the flowering time, lanceolateoblong, acute or acuminate, to 60 × 15 cm, glabrous; petioles 5-6 cm long. Inflorescences arising from the base or middle of the pseudobulb, erect at the base and nodding in the apical part, softly pubescent; peduncles 36-50(-75) cm long; sterile bracts 5-12, scattered along the flowering stem and a few clustered at its base, erect or suberect, lanceolateoblong, acute or acuminate, (1.5-) 2.7-6.5 cm long, pubescent or sparsely pubescent, sheathing, occasionally decayed at the flowering time and only the leaf scar visible; raceme lax or semi-dense, 5- to many-flowered; rachis gradually increasing in length for some time (fide Seidenfaden & Wood 1992), 10- 30 cm long; floral bracts persistent, ovate-lanceolate, long-acuminate, (10-)14-22 × (4-) 6-11 mm, much shorter than the pedicel plus the ovary, pubescent. Flowers 15-20(-23) mm across, pink or purple, often with a red throat, rarely white, gynostemium light violet, operculum cream, spur light green to light brown. Ovary indistinguishable from the pedicel, 23-35(-45) mm long, pubescent. Sepals ovate-lanceolate, acute or apiculate, 3- or 5-veined, outside pubescent, inside glabrous or with scattered hairs; median sepal (11-)13-17 × 3.7-6(-8) mm; lateral sepals reflexed, (11-)13-16(-18) × 3.5-6(-7.7) mm. Petals obovate-elliptic, obtuse, apiculate, 3- to 7-veined, (10-)11-16 × 4-8(-10.5) mm, glabrous or with scattered hairs. Lip 3-lobed, (10-)15-20- (-28) × (10.5-) 20-26 mm, base completely united with the gynostemium, sometimes with two small auricles at the base of the free portion, without prominent ornaments but basal part sometimes with three obscure longitudinal ridges, spurred, glabrous or with scattered hairs; midlobe (3-)4-7 × 5-11(-12.5) mm, deeply emarginate with two elongate oblong and spreading lobules, sinus obtuse, to 3 mm deep, sometimes with a tiny tooth; side lobes oblong, obtuse, spreading, (3-)4-6(-8) × 2.3- 5(-9) mm, not much widened towards the apex; spur cylindric, pointing backwards at the base and strongly curved forwards above, pubescent, 13-20(-21) mm long. Gynostemium 4-7(-8) mm long, glabrous; rostellum bilobed. Fruits ellipsoid, 17-23 × 6-10 mm.

DISTRIBUTION AND PHENOLOGY

Widespread but scattered in most parts of Thailand except the Northern , North-Eastern and South- Western regions. Also recorded in Indochina , the Philippines and Peninsular Malaysia. The species is found on rocks in evergreen forest, often associated with limestone and sometimes on the edge of evergreen swamp forest, from sea level to 800 m. Flowering mainly from December to February .

REMARKS

Diagnostic characters of this species are the medium-sized pink flowers with bilobulate lip midlobe and spreading side lobes. It is thus rather similar to C. vestita but differs in its flower colour and size. A further difference is the primarily epilithic growth ( C. vestita is mainly epiphytic).

The collection Kerr 0122 from Saraburi was originally identified as Calanthe vestita Lindl. and later also listed as such by Seidenfaden (1975: 30). Its pink flowers and the short sepals (10-12 mm) are not known in this species but fit the concept of C. rubens . However, the single remaining flower of the collection is very unusual in its lip shape, having side lobes which are much longer and wider than the lip midlobe.

Seidenfaden & Smitinand (1961) report on a white form found in Surat Thani Province (Peninsular Thailand).

Figures

FIG. 2. — Calanthe rubens Ridl.: A, C, flower; B, top part of gynostemium. A, B, Thai plant, Seidenfaden & Smitinand 6487; C, Philippine plant, Weber 406. Reproduced with permission from the University of Copenhagen, drawn by Kai Olsen. Scale bars: A, C, 1 cm; B, 3 mm.