Hilsenbergia apetala J.S. Mill., 2003

Miller, James S., 2003, Classification of Boraginaceae subfam. Ehretioideae: Resurrection of the genus Hilsenbergia Tausch ex Meisn., Adansonia (3) 25 (2), pp. 151-189 : 160-162

2. Hilsenbergia apetala J.S. Mill. , sp. nov.

Frutex vel arbor parva , cortice subtiliter fissurata, ramunculis sparse puberulis vel glabris. Folia decidua, alterna vel sub-opposita, lamina ovata ad elliptica , 2.5-5.5 cm longa, 1.3-3 cm lata, apice acuminata usque acuta vel raro obtusa , basi acuta usque obtusa vel rotundata , margine integra, adaxialiter glabra vel trichomatibus secus costam vestita , abaxialiter puberula vel glabra ; petiolo 5- 17 mm longo. Inflorescentiae terminale, racemosae vel cymosae, 1.5-5.5 cm longae. Flores bisexuales; calyce campanulato usque urceolato, 3-3.5 mm longo, 5-lobo, glabro praeter trichomatum caespites ad apices lobulorum; corolla tubularis, lobis absentibus. Fructus non visi.

TYPUS. — Service Forestier: SF24232 (Capuron), Madagascar, Prov. Mahajanga (Ambongo), calcaires, près d’un cours d’eau, au sud d’Antsakoamanera, baie de Marambitsy, 16°30’S, 44°40’E, fl., 20 Nov. 1965 (holo-, P!; iso-, G!, GH!, K!, MO!, P!, TEF!, WAG!) .

Shrub or small tree, the bark finely fissured, the twigs sparsely puberulent to glabrous; leaves deciduous, borne only on the current season’s growth, alternate to subopposite; blades ovate to elliptic, 2.5-5.5 cm long, 1.3-3 cm wide, the apex acuminate to acute or rarely obtuse, the base acute to obtuse or rounded, the margin entire, the adaxial surface glabrous or with hairs along the midrib, the abaxial surface evenly puberulent to glabrous, the venation brochidodromous, the midrib even with the adaxial surface or impressed near the base, raised on the abaxial surface, the secondary veins 3-5, the tertiary venation reticulate; petioles 5-17 mm long, narrowly canaliculate on the adaxial surface, glabrous but puberulent in the channel.

Inflorescences terminal, racemose or cymose, but branched only slightly toward the base if at all, 1.5-5.5 cm long, the branches glabrous to puberulent. Flowers bisexual; calyx campanulate to urceolate, 3-3.5 mm long, 2-3 mm long, 5- lobed, the lobes somewhat uneven, triangular, 1- 1.5 mm long, glabrous on both surfaces but with minute tufts of hairs at the apex of the lobes; corolla tubular, included in the calyx or only shortly exserted, 2-3.5 mm long, lacking lobes; stamens 5, the filaments 2.5-5.5 mm long, adnate to the corolla for its full length, the upper 0.3-2.5 mm free, the free portion winged, the anthers ellipsoid, 1-2 mm long; ovary conical, 1- 1.5 mm long, 1 mm wide, the style 2-3 mm long, the 2 stigmas capitate. Fruits unknown. — Fig. 3 .

Hilsenbergia apetala is a strikingly distinct species, easily recognized by its highly reduced corolla, which lacks lobes and has the staminal filaments adnate to it for its full length. It thus appears as though the staminal filaments are fused into a tube and no corolla is present. I am not aware of any other member of the Ehretioideae with this floral structure. It is also unusual in its nearly racemose inflorescence, which is usually reduced to a simple rachis, or occasionally has a few, highly-reduced lateral branches.

DISTRIBUTION. — Hilsenbergia apetala occurs in western Madagascar ( Fig. 2 ) where it grows on calcareous substrates.

VERNACULAR NAME. — Hazodomohina.

CONSERVATION STATUS. — Provisional IUCN Red List Category: Endangered (EN B2ab(i-iv)). Hilsenbergia apetala is known from the tsingy of Namoroka and Bemaraha, both protected as Réserves Naturelles Intégrales. Populations outside of the two protected areas certainly face immediate threat. Further fieldwork will be necessary to document the size of populations within the protected areas; the reserves at Bemaraha and Namoroka are very poorly collected, so the limited number of available specimens may not prove rarity.

PARATYPES. — MADAGASCAR: Jongkind 3280, Prov. Mahajanga, Tsingy de Bemaraha , RHI, N of the Manambolo River, 50 m, 19°09’S, 44°49’E, fr., 29 Nov. 1996 ( MO!); Perrier de la Bâthie 17867, Prov. Mahajanga, Réserve Naturelle de Namoroka , Ambongo, 16°26’S, 45°22’E, fl., Dec. 1926 ( MO!, P!); Réserves Naturelles: RN5617, Prov. Mahajanga, Réserve Naturelle 8, Namoroka, dist. Soalala, Canton Andranomavo, 16°26’S, 45°22’E, fl., 31 July 1953 ( P!, TEF!); Service Forestier: SF12008 (Tata) , Prov. Mahajanga, forêt d’Antsingy, Réserve Naturelle de Bemaraha, Antsolova , 150-750 m, 18°35’S, 44°47’E, fl., 23 Oct. 1954 ( P!) .

Figures

Fig. 3. — Hilsenbergia apetala J.S. Mill.: A, flowering branch with leaves; B, flower; C, open flower with calyx and corolla opened to show that the corolla is reduced and lacks lobes; D, dorsal view of pyrene; E, cross-section of dorsal surface of pyrene. Service Forestier: SF24232 (Capuron). Drawn by A. JOUY.

Fig. 2. — Distributions of Hilsenbergia species, mapped on the simplified bioclimate zones of Madagascar (after CORNET 1974; see SCHATZ 2000).