Angraecum cornigerum Jacob de Cordemoy (1899: 418)

Pailler, Thierry, Verlynde, Simon, Bytebier, Benny, Florens, F. B. Vincent & Baider, Cláudia, 2020, Revision of Angraecum sect. Perrierangraecum (Orchidaceae; Epidendroideae; Vandeae) for the Mascarenes, with a description of a new endemic species for Mauritius, Phytotaxa 442 (3), pp. 183-195 : 188-189

3. Angraecum cornigerum Jacob de Cordemoy (1899: 418) . ( Fig. 2C )

Homotypic synonym:— Pseudojumellea cornigera (Cordem.) Szlach., Mytnik & Grochocka in Szlachetko et al. (2013: 21). Type:— RÉUNION. Cilaos, bras de Benjoin, environs des eaux thermales, Cordemoy s.n. (lectotype P00750178!).

Description:— Plants epiphytic, erect or pendulous with age; stem sometimes branched, up to 500 mm long, covered with old leaf sheaths; leaf sheaths reticulate, rough; internode 10–20 mm. Roots few, sub-basal to basal, thick, verrucose, white-greyish. Leaves 4–12, erect, distichous, 30–80 × 2–4 mm, linear, coriaceous, rough, dark green with bluish tinge, slightly V-shape, sub-cylindrical, canaliculate on both sides, acute, sometimes recurved. Inflorescences 1 to 2, single-flowered. Peduncle 40–60 mm long, covered by 2 to 3 membranous sheaths; sheaths 3–7 mm long, striate, thin. Floral bracts (1–) 6–7 mm long, semi-amplexicaul, striate, keeled. Flower resupinate, 40–70 mm diameter, white, sometimes with green tinge, slightly fleshy, nectariferous with only few drops of nectar present, odourless. Sepals 40–45 × 8–9 mm, narrowly-ovate, acuminate; similar to each other; median sepal slightly narrower than laterals. Petals 35 × 4 mm, narrowly-ovate. Labellum 35–40 × 18–25 mm, largely ovate, long-acuminate. Spur 130–150 mm long, filiform, pendent. Rostellum abnormally developed. Pollinia in direct contact with stigma (autogamy). Ovary (including peduncle) 40–60 mm long, narrow at the base. Capsule triquetrous, apex truncate, 30–40 × 18–22 mm, long lasting; peduncle 10 mm long.

Distribution:— Réunion,? Madagascar. The species is likely present on Madagascar ( Andriananjamanantsoa et al. 2016), but collection of flowering material is necessary to determine its identity.

Habitat and ecology:— Found in mid to high-elevation native forests in the north of the island, also in the calderas (‘cirque’), between 850–1950 m elevation ( Fig. 3E ). Usually growing as an epiphyte in the crown of canopy trees and difficult to detect. Although having a large elevational range, it occurs infrequently and in low densities in any given locality ( Jacquemyn et al. 2007). The species is autogamous, with high fecundity and flowers are open for 1 to 2 days only. On Madagascar, the putative specimens were collected in the central highland ( Andriananjamanantsoa et al. 2016), in an area where small native vegetation patches survive within a matrix of anthropogenic landscape (Andriananjamanantsoa, pers. comm., 14 April 2020).

Conservation status:— A species considered rare since it was described by Jacob de Cordemoy (1899) and known from only a few populations with low numbers, despite being autogamous. Its Area of Occupancy is 36 km 2 and its Extent of Occurrence is 171 km 2. Given its limited distribution (four localities using ConR version 1.2.4) and the fact that although its main habitat is protected as part of the National Park of La Réunion, invasion by alien plants is progressing ( MacDonald et al. 1991; MacDonald 2010), thereby modifying its habitat away from what it requires, the suggested conservation status is EN B1a(iii)+B2ab(iii). On Madagascar, few individuals were found in a single site, where remnant patches of forests are mostly degraded by past collection of firewood, but illegal orchid collection is ongoing (hence details not given), and where fires are a threat, especially for Angraecinae orchids ( Whitman et al. 2011). Therefore, the suggested assessment would still hold, with a small increase of values of AOO and EOO.

Phenology:— Flowering in November and December.

Additional specimens examined:— RÉUNION. Col de Bébour , 1400 m, 15 January 1973, fl., Cadet 4024 ( REU008026 ) ; Grand Matarum , 1450 m, s.d., fr., Girard s.n. ( P00754623 ) ; Mare à Joseph, 1400 m, 20 January 1978, fr., Cadet 5934 ( REU008029 ) ; 1400 m, fl., 1 January 1979, Cadet 5948 ( REU008030 ) ; 1400 m, 20 December 1981, fr., Cadet 6324 ( REU008028 ) ; 1400 m, 7 January 1982, fl., fr., Cadet 6330 ( REU006330 , REU008012 , REU008027 ) ; Montée de la Plaine des Chicots , February 1971, fr., Bosser 20688 ( P00754422 ) ; Plateau des Fraises , 1950 m, 17 January 2009, fl., Pailler TP 273 ( REU010121 ) ; Sentier Hell Bourg Cap Anglais , ravine après plantation de Cryptoméria, 21 June 2009, fr., Martos FM 725 ( REU007746 ) ; 21 June 2009, Martos FM 730 ( REU007744 ) ; Audessus des Thermes de Cilaos , 1450 m, 23 February 1975, fr., Cadet 5064 ( REU008031 ) ; s. loc., 2 September 1988, fl., Dupont 5 ( P00754734 ) .

Figures

FIGURE 2. Angraecum sect. Perrierangraecum of the Mascarenes.A. Angraecum cucullatum. B. Angraecum liliodorum. C. Angraecum cornigerum. D. Angraecum borbonicum. E. Angraecum baiderae. Photos: A, C, D. Frederic Henze; B. François Vandeschricke; E. F.B. Vincent Florens.

FIGURE 3. Distribution of the five species of Angraecum sect. Perrierangraecum on the islands of the Mascarenes. A. Angraecum baiderae (Mauritius). B. Angraecum borbonicum (Réunion). C. Angraecum cucullatum (Réunion). D. Angraecum cucullatum (Mauritius). E. Angraecum cornigerum (Réunion). F. Angraecum liliodorum (Réunion).