Benthamia arcuata (H.Perrier) Descourv. & Hervouet, 2025

Hervouet, Jean-Michel, Descourvières, Pascal, Hermans, Johan & Longou, Ludivine, 2025, Revision of the genus Benthamia A. Rich. (Orchidaceae, Orchidioideae, Habenariinae), Adansonia (3) 47 (11), pp. 171-249 : 182-183

Benthamia arcuata (H.Perrier) Descourv. & Hervouet , comb. nov., stat. nov.

( Figs 8 ; 9)

Benthamia herminioides subsp. arcuata H.Perrier , Bulletin de la Société botanique de France 81 ( Perrier 1934: 36).

TYPE MATERIAL. — Madagascar • Diana, Mt.Tsaratanana ; 14°01’17”S, 48°57’60”E; alt. 2600-2880 m; IV.1924; H. Perrier 16477; holotype: P [ P00094514 ] !.

ETYMOLOGY. — From Latin “ arcuatus ”, curved like a bow, in reference to the shape of the ovary.

PHENOLOGY. — April and October-November.

DISTRIBUTION AND ECOLOGY. — Madagascar. In montane ericoid thicket, in the north between 1850 and 2150 m ( Fig. 10 ). Benthamia herminioides subsp. arcuata is listed by Szelengowicz & Tamon (2013: 245) for La Réunion. The text refers to the Madagascan species but the two photographs show Benthamia perfecunda on the left and Benthamia mascula sp. nov. on the right.

CONSERVATION. — So far known only from Mt. Marojejy in Sava region and Mt. Tsaratanana in Diana region, the two northernmost regions in Madagascar. On Marojejy it grows in a very confined area but within a National Park. In view of our observations in Mt. Marojejy, it is considered Vulnerable ( VU) according to criterion D1, number of mature individuals fewer than 1000. The population of Mt.Tsaratanana has not been documented since its discovery in 1924.

ADDITIONAL SPECIMENS EXAMINED. — Madagascar • Sava, sommet oriental du massif de Marojejy; 14°26’48”S, 49°44’06”E; alt. 1850-2137 m; 26.III-2.IV.1949; H. Humbert et al. 23755; P [ P00692986 , P00692987 ]!, G • Sava, district d’Andapa, Massif du Marojejy; 14°26’48”S, 49°44’06”E; alt. 2000-2137 m; XI.1972; P. Morat 4025; P [ P00692452 ] ! • Sava, district d’Andapa, Massif du Marojejy; 14°26’48”S, 49°44’06”E; alt. 2000-2137 m; XI.1972; P. Morat 4039; P [ P00692453 ] ! • Sava, district d’Andapa, camp n°5, on the summit of Marojejy; 14°26’48”S, 49°44’06”E; alt. 2100 m; XI.1996; N. Messmer et al. 372; P [ P02103086 ]!, K [ G00163180 ]!, MO, S • Sava, district d’Andapa, RNI de Marojejy; 14°26’48”S, 49°44’06”E; alt. 2000-2137 m; 16.XI.1996; M. Rakotondrainibe 3694; P [ P01778632 ] ! • Sava, district d’Andapa, RNI de Marojejy; 14°26’48”S, 49°44’06”E; alt. 2050 m; 22.XI.2003; H.H. Schmidt et al. 4263; MO [ MO3022641 ] !.

NOTES

Perrier noted that the lateral lobes of lip are narrow and acute, which could not be verified on the type. The species was first described as a sub-species of Benthamia herminioides Schltr. but is readily distinguished by the larger flowers, the fleshy and thick floral parts and the very prominent callus on the lip. Specimens from Mt. Marojejy and Mt. Tsaratanana should be compared when fresh material becomes available from the latter locality. There is no obvious difference in dry material but the flowering seasons are different.

See also: Perrier (1939: 37), Cribb & Hermans (2009: 48).

DESCRIPTION

Erect terrestrial herb, 19-35 cm tall. Tubers 15-20 × 5 mm, 4- 7 roots up to 7 cm long, 3 mm in diameter. Stem erect, 1-2.5 mm in diameter, green, with 2-5 sheaths regularly spaced. Leaves 1-2, basal, 30-50 mm × 10-20 mm, narrowly ovate to ovate, acute, coriaceous, glossy. Rachis 4-12 cm, mostly secund, shorter than half of the inflorescence, bearing 10-30 flowers 2-5 mm apart. Floral bracts lanceolate, acuminate, 5-6 mm long, smaller or only slightly longer than the ovary. Ovary fusiform, curved at apex, 4-6 mm long. Flowers at right angle to ovary, hardly opened, campanulate, 2.5-4 mm long, all floral parts fleshy and thick, yellowish green; dorsal sepal, slightly apiculate at apex, concave, oblong, 2-2.3 × 0.8-1.2 mm; lateral sepals spreading, oblong or slightly obovate, navicular, green, 2 × 0.8-1 mm; petals oblong, adnate to the dorsal sepal, 1.9-2 × 1-1.1 mm, apex sub-acute to obtuse, slightly asymmetric, forming a hood with the dorsal sepal; lip 2-3 × 1-1.8 mm, with a very prominent longitudinal callus, trilobed, lateral lobes 0.3- 1 × 0.5-0.7 mm, midlobe 0.5-1 mm × 0.5-0.7 mm; spur curved, adpressed to the ovary, 0.6-0.8 mm long, slightly bilobed. Column subterete, 0.6-1 mm high, 0.5 mm in diameter, with a short apiculus at apex; rostellum trilobed, short, with midlobe rounded; auricles strap-shaped, half the column length.

Figures

FIG. 8. — Benthamia arcuata (H.Perrier) Descourv. & Hervouet, comb. nov., stat.nov.,Mount Marojejy,Madagascar,29 October 2005.Flowers.Photograph by Jean-Michel Hervouet.

FIG. 10. — Distribution map ofBenthamia arcuata(H.Perrier) Descourv.&Hervouet,comb.nov.,stat.nov.