Benthamia decaryana 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 : 192-194

Benthamia decaryana Descourv. & Hervouet , sp. nov.

( Figs 27 ; 28 ; 29 )

DIAGNOSIS. — This species has broadly similar flowers to those of Benthamia africana but the habit is smaller (largest plant known 35 cm high vs 62 cm). The most distinctive difference lies in the fact that leaves are all basal, less than 5 cm long, conduplicate, coriaceous, generally with undulate margins and arcuate, at least when dried (vs leaves linear or ligulate, 6-18 cm long, remaining flat when dried). The rostellum has a very wide and large midlobe, 0.4-0.5 mm long, protruding and pointing downwards (vs midlobe 0.1-0.2 mm).

TYPE MATERIAL. — Madagascar • Atsimo-Atsinanana, Midongy du sud ; 23°35’S, 47°01’E; 23.VIII.1926; R. Decary 5138; holotype: P [ P00094591 ]!; isotypes: P [ P00094592 ]!, K!, TAN !.

ETYMOLOGY. — Named for Raymond Decary (1891-1973), colonial administrator in Madagascar. He undertook seven scientific missions from 1922 to 1944, collecting, among many other things, 40000 specimens of plants.

PHENOLOGY. — September.

DISTRIBUTION AND ECOLOGY. — Madagascar. Known only from the Atsimo-Atsinanana region, therefore the south-east, in forest on laterite soil. A humid roadside is mentioned on the type specimen ( Fig. 28 ).

CONSERVATION. — This species has been collected only twice and has not been recorded since 1926. However, the locus classicus, South Midongy, is not very accessible. With only two known locations and the continuing decline of the forests in the region it must be considered Endangered (EN) under criterion B1.

ADDITIONAL SPECIMENS EXAMINED. — Madagascar • Atsimo-Atsinanana, Vondrozo ; 22°49’14”S, 47°19’10”E; 5.IX.1926; R. Decary 5195; P [ P00094587 ] !.

NOTES

This small species has a strikingly distinctive rostellum compared with other Benthamia species. The most distinctive difference is however the short basal conduplicate leaves, which are unique among other Benthamia .

DESCRIPTION

Erect terrestrial herb, 12-23(35) cm tall. Tubers 1-2, ovoidfusiform, 2-3 cm long. Stem 0.8-1.8 mm in diameter, with basal leaves and then 2-4 linear acute sheaths 5-30 mm long. Leaves 3-5, basal, 2-5 × 0.3-0.8 cm, conduplicate, slightly thick and coriaceous, often with undulate margins when dried. Rachis 6-21 cm long, with 10-37 flowers, at an average distance of c. 5 mm from each other. Floral bracts lanceolate-acuminate, 1.5-7 × 0.8-2 mm, shorter than the ovary except the lower ones, which can be a little longer. Ovary fusiform, 4-6 mm long to 8 mm when mature. Flowers small, greenish, about 2-2.5 mm long; dorsal sepal elliptic-oblong, obtuse, 2.2-2.5 × 0.8 mm; lateral sepals elliptic-oblong, subacute, 2.2-2.5 × 0.7 mm; petals 2.2 × 1.2-1.3 mm, as long as the sepals but wider, oblong, obtuse, thickened at the apex, lip concave at the base, 2.2-2.8 × 1.5 mm, trilobed at the apex, with midlobe broadly triangular, 0.7-0.8 × 0.5 mm, lateral lobes shorter, 0.3-0.5 mm wide; spur scrotiform, 0.5 × 0.6 mm. Column 0.8 × 0.5 mm, anther subterete, obtuse; auricles slightly falcate, subcrenulate, 0.5 mm long, as long as the anther, rounded at apex; rostellum trilobed, very unusual for the genus, with a large, fleshy and protruding downward pointing midlobe, 0.3-0.4 mm long, lateral lobes obtuse, shorter than the midlobe.

Figures

FIG. 27. — Benthamia decaryana Descourv. & Hervouet, sp. nov.: drawing of the column by Pascal Descourvières, showing the auricle and the rostellum.

FIG. 28. — Distribution map of Benthamia decaryana Descourv. & Hervouet, sp. nov.

FIG. 29. — Benthamia decaryana Descourv. & Hervouet, sp. nov.: drawing by Ludivine Longou, after dried specimens: A, habit; B, side view of part of the rachis. Scale bars: A, 10 mm; B, 5 mm.