AFRICAN

ORCHIDS

Aeranthes unciformis P.J.Cribb & Nusb., Candollea 67: 272 (2012).
Description:
An epiphyte herb on trees with a very short stem; roots adventitious, slender, 1-1.5 mm in diameter. Leaves 4-5, distichous, twisted at the base to lie in one plane, oblanceolate oblong, obtusely obliquely bilobed at the tip mostly with a longer distal lobe and a shorter proximal lobe, 6-8 x 0.9-2 cm, articulated at the base to a short conduplicate leaf base. Inflorescences much shorter than the leaves, axillary, 1- to 3- flowered, 25-30 mm long; peduncle terete, 10-12 mm long; bracts small, ovate, acuminate, 4-4.5 mm long. Flower resupinate, large for the size of the plant, translucent, white; pedicle and ovary 20 mm long, scabrid. Dorsal sepal curving forwards over the column and lip, linear-tapering, longly caudate, 65-85 x 3 mm; lateral sepals spreading-decurved, falcate at base, linear-tapering, longly caudate, 55-60 x 4.5-5 mm. Petals spreading upwards, linear-tapering, caudate, 29-30 x 5-6 mm. Lip ecallose, somewhat porrect, concave, broadly ovate, caudate, ciliate along the margin of the tapering part, 38-50 x 20- 22 mm; spur with a broad mouth then narrowly cylindrical, straight, 22-24 mm long. Column 5 mm long, with two recurved lateral arms at the tip, each 2 mm long; anther cap broadly cordiform; viscidia 2, strap-like, 2 mm long.
Etymology:
The specific epithet refers to the morphology of the dorsal sepal curving forwards over the column and lip.
Notes:
Aeranthes unciformis is very distinct in the genus. It has the habit of A. laxiflora Schltr., a widespread species in the Mountains of Madagascar, but quite different and much larger flowers. Its flowers are somewhat reminiscent of those of A. caudata Rolfe but much larger with longer acumens and are borne two or three at a time in a short inflorescence, rather than appearing in succession on slender elongate wiry branching peduncles. The lip is very distinctive, almost transversely elliptic at the base then drawn out and tapering into a long acumen at the tip. The spur, 22-24 mm long, is also much longer than in most Aeranthes species. The dorsal sepal is very peculiar, curving forwards over the column and lip.
Habitat and ecology:
Aeranthes unciformis was recorded in dry deciduous forest close to a seasonal river at 170 m elevation. This epiphytic plant occurs on trunks of trees at 2 to 4 m above ground. It grows in forests with canopies reaching 8 to 12 m, with emergent trees reaching 14 m, with an shrub stratum at 3 to 5 m high, and a sparse suffrutescent stratum less than 0.5 m high. Flowering time. – February.
Cultivation:
As given for the genus.
Distribution:
The species is only known from the type locality in the northern part of the Bekaraoka forest in the Loky-Manambato region in North-East Madagascar.
References:
Angraecum Darainense P. J. Cribb & Nusb. and Aeranthes Unciformis P. J. Cribb & Nusb. (Orchidaceae), Two New Species from Northern Madagascar, Candollea 67(2) • December 2012; WCSP (2017). 'World Checklist of Selected Plant Families. 21.01-2017; http://apps.kew.org/wcsp/
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