Jumellea Schltr.

Rakotoarivelo, Fanny, Pailler, Thierry & Faliniaina, Lucien, 2013, Revision of the genus Jumellea Schltr. (Orchidaceae) from the Comoros Archipelago, Adansonia (3) 35 (1), pp. 33-46 : 36-37

Genus Jumellea Schltr.

Die Orchideen: 609 (1914); Perrier de la Bâthie in Humbert H. (éd.), Flore de Madagascar, 49 e fam., Orchidées 2: 157 (1941); Du Puy et al., hve Orchids of Madagascar, 1 st éd. (1999); Stewart et al., Angraecoid orchids: 186 (2006); Hermans et al., Orchids of Madagascar 2nd éd. (2007); Cribb & Hermans, Field Guide to the Orchids of Madagascar (2009).

— Type: Jumellea fragrans (Thouars) Schltr. , Die Orchideen: 609 (1914).

DESCRIPTION

Epiphyte or lithophyte, rarely terrestrial; stem absent or elongated; leaves frequently distichous, generally oval or oblong, conduplicate at the base or along the whole leaf length, relatively bilobate-obtuse at the apex. Easily recognized by their single-flowered inflorescences delivered simultaneously at flowering; inflorescences appear in the upper part of the stem, piercing or emerging from old foliar sheaths. Peduncle covered by 4-6 sterile bracts at the base ( Fig.2A ), separated from the pedicel by a tubular or sigmoid-shaped (upcurved and acuminate at the apex) fertile bract. The fertile and sterile bracts have the same shape but differ in size. The sterile bracts increase in size following the order of their apparition, the last are mostly the same size as the fertile bract. Flower white or cream-colored, changing to clear yellow with age or after pollination. Median sepal triangular often upright or inverted backwards; lateral sepals connected at the base below the spur, projecting forwards with petals and lip, giving a particular shape to the flower.Petals narrow, as long as the sepals. Lip always contracted at the base, sometimes gutter-shaped, and connected to the spur. Lip shape is ovate, lanceolate or sagittate ( Fig. 2C ). Sometimes an ovate lip may display widened part on the edge that forming a pandurate shape. Therefore both an ovate- and pandurate-shaped lip can sometimes be observed in one species or on one plant.A lanceolateshaped lip can vary in one species.The widest part of the lip can be placed near the base, in the middle or near the apex. The sagittate-shaped lip differs from the two former lip shapes by the abrupt contraction of the lip just after the widened part. This widened part has mostly a rounded edge and an acute or acuminate apex.Column dilated at the base, extended in two parallel arms related, on the internal side, to the edges of the orifice of the spur and, on the external side, to the lateral sepals. Anther covered by a removable cap and excised in to two naked pollinia. Pollinia attached to two viscidia (modified part of the rostellum) by a retractable caudicle, free or barely adhesive to the base. Rostellum divided on two large lobes, joined in the middle, protruding forward as a tunnel-shaped entrance facilitating pollinators visit and support to the anther cap; median tongue of the rostellum rarely absent, dentiform, appearing between the lobes of the rostellum. Inferior ovary connected directly to the pedicel called pedicellate ovary, often longer than the peduncle. Spur length varies between 6 to 150 mm.

Jumellea species are most of the time found in humid or rocky habitat. They are distributed along a wide elevation range, extending from coastal region to high mountain sites. The genus is present in the four islands of Comoros archipelago ( Table 1 ), the highest record is at 2200 m above sea level in the volcanic mount of Karthala (2361 m) on Grande Comore.

Figures

FIG. 2.— Flower description of Jumellea Schltr.:A, inflorescence;B, flower;C, lip shape;C1, ovate or pandurate;C2, lanceolate;C3, sagittate; D, side view of the column; E, inner view of anther;F, pollinia. Abbreviations:ms, median sepal; ls, lateral sepal; pt, petal;lp, lip; ac, anther cap; lr, lobe of the rostellum; ar, arm of the column; sp, spur; fb, fertile bracts; sb, sterile bracts. Scale bars: A, C, 1 cm; B, 6 mm; D, 3 mm; E, 2 mm; 1 mm.