Oeceoclades Lindl.

Orchidaceae, I. la Croix & P.J. Cribb. Flora Zambesiaca 11:2. 1998

Habit

Terrestrial herbs, rarely epiphytic.

Pseudobulbs

Pseudobulbs set close together, heteroblastic, ovoid to fusiform, 1–3-leaved at the apex.

Leaves

Leaves coriaceous, conduplicate, not plicate, often variegated, usually petiolate with the petiole articulate above the base.

Inflorescences

Inflorescences arising from base of the pseudobulb, simple or branched, several- to many-flowered.

Flowers

Flowers resupinate, relatively small, thin-textured.

Calyx

Sepals and petals free, variously spreading, subsimilar, the petals usually shorter and broader than the sepals.

Labellum

Lip spurred, 3-lobed, the mid-lobe usually 2-lobed or emarginate so that the lip appears 4-lobed; disk either with 2 quadrate or triangular calli at the mouth of the spur or with 3 variously thickened, parallel ridges which, together with the lateral veins, are sparsely but distinctly papillose or hirsute.

Column

Column erect, rather short, oblique at the base; anther cucullate or cristate; pollinia 2, ovoid or pyriform, on a short or rudimentary stipes; viscidium large; stigmata confluent; rostellum short.

Distribution

Oeceoclades comprises about 50 species, widespread in Madagascar and the African tropics. It is also found in tropical Asia, the southwestern Pacific islands, Australia, and recently the Neotropics. The centre of diversity lies in Madagascar. Oeceoclades pulchra (Thouars) M.A.Clem. & P.J.Cribb ranges from tropical Africa and Madagascar to tropical Asia, Australia, and the southwestern Pacific islands. Oeceoclades maculata (Lindl.) Lindl. is widespread in the tropical Americas as well as tropical Africa and Madagascar. Stern (1988) reasoned that this species originated in Africa and may have then seeded across the Atlantic in the Paleocene (54 million years ago) when Africa and South America were only 500 miles apart and spanned by volcanic islands, promoted by the development of autogamy; this hypothesis can be discounted due to the low levels of genetic divergence in this genus. It has to be a recent long-distance dispersal, perhaps man-assisted. It is weedy and is actively expanding its range. (PC, AP).

Ecology

Many coriaceous-leaved species grow in sandy soils in dry forests and scrub at sea level and slightly higher elevations inland. A few coriaceous-leaved species are found in dry tropical forests on limestone in karst areas. The plicate-leaved species are found in moister tropical evergreen forests, often in montane and low-elevation forests, from sea level to 1400 m. (PC).

General Description

Terrestrial herbs, rarely epiphytic.Pseudobulbs set close together, heteroblastic, ovoid to fusiform, 1–3-leaved at the apex.Leaves coriaceous, conduplicate, not plicate, often variegated, usually petiolate with the petiole articulate above the base.Inflorescences arising from base of the pseudobulb, simple or branched, several- to many-flowered.Flowers resupinate, relatively small, thin-textured.Sepals and petals free, variously spreading, subsimilar, the petals usually shorter and broader than the sepals.Lip spurred, 3-lobed, the mid-lobe usually 2-lobed or emarginate so that the lip appears 4-lobed; disk either with 2 quadrate or triangular calli at the mouth of the spur or with 3 variously thickened, parallel ridges which, together with the lateral veins, are sparsely but distinctly papillose or hirsute.Column erect, rather short, oblique at the base; anther cucullate or cristate; pollinia 2, ovoid or pyriform, on a short or rudimentary stipes; viscidium large; stigmata confluent; rostellum short.

Terrestrial or rarely lithophytic herbs. Roots basal. Perennating organ stem-like or pseudobulbous, cylindrical, fusiform, conical or ovoid, heteroblastic, often angular in cross-section. Leaves linear, lanceolate, ovate or elliptic, acute to acuminate, conduplicate and coriaceous or plicate, articulate at base, usually petiolate, green or mottled with light and dark green, rarely flushed with purple. Infl orescence lateral, usually exceeding leaves, simple or branching; bracts inconspicuous, persistent, rarely with an extrafl oral nectary. Flowers white, yellow, green or brown, sometimes purplestriped; labellum white or yellow with purple venation. Dorsal sepal free, erect to porrect, obovate to spatulate; lateral sepals oblique at base, otherwise similar to dorsal sepal. Petals free, similar or dissimilar to sepals, obovate to elliptic-oblong, often broader than sepals, often porrect. Labellum free to base, trilobed, spurred at the base, callose, lateral lobes free to base of column, midlobe fl at or convex; callus two- or three-ridged. Column with a distinct foot; pollinia two, ovoid or pyriform. Ovary cylindrical, grooved. (PC).

Terrestrial, rarely epiphytic herbs. Pseudobulbs close together, usually ovoid to fusiform, ± approximate, usually heteroblastic (with only one internode elongated, the remaining basal ones very short), apex 1–3-leaved, up to 15 cm. long and 3 cm. broad, but often narrower. Leaves usually with duplicate vernation, coriaceous, conduplicate, often variegated, usually petiolate, the petiole articulate some distance above the base and sometimes above the middle, the line of articulation consisting of a number of irregular blunt or acute teeth or occasionally ± regular. Inflorescences arising from the base of the pseudobulb, often exceeding the leaves, simply racemose or frequently paniculate; bracts inconspicuous, rarely with a basal extrafloral nectary. Flowers resupinate, rather small, thin in texture. Sepals and petals free, variously spreading, similar, the petals usually slightly shorter and broader. Lip decurved, spurred, 3- or apparently 4-lobed; side lobes erect; mid-lobe usually lobulate or emarginate; disc either with 2 approximate, quadrate or triangular calli at the spur entrance or with 3 variously thickened, parallel ridges which together with the lateral nerves are sparsely but distinctly papillose or hirsute. Column erect, short, oblique at the base or with a short foot; anther cucullate or cristate; pollinia 2, ovoid or pyriform, on a short or rudimentary stipe; viscidium large; stigmata confluent; rostellum short.