Leafless epiphytic or rarely lithophytic herbs with short stems. Roots firmly or loosely attached to the substrate, often dense, terete or less commonly dorso-ventrally flattened, smooth or rarely verrucose, unbranched or with a few branches, usually elongate. Scales on stem protecting the stem apex, acute to rostrate. Inflorescences few–many, axillary, racemose, concentrated in the apical part of the stem, few–many-flowered; peduncle long or short; rhachis terete or angular, smooth or with processes; bracts sheathing or not. Flowers small to minute, ± sessile or pedicellate, usually white variously tinged with green, brown or pink on spur and other segments. Sepals and petals free, subsimilar. Lip entire or obscurely 3-lobed, free, usually with fleshy calli at the base either side of the mouth of the spur; spur globose, cylindrical or variously swollen. Column fleshy; androclinium short to long; anther-cap hemispherical, often elongated at the apex; pollinia 2, subglobose to pyriform; stipes linear to oblanceolate, entire or bifid at the apex; viscidium linear or oblong, short to long; rostellum bifid, short to as long as the column.
Epiphytic aphyllous herbs, rarely epilithic.Stems usually unbranched, bearing numerous scale leaves and roots, the living part short but sometimes with an elongated dead part at the base.Scale leaves acute to rostrate, protecting the stem apex.Roots firmly or loosely attached to substrate, branched or unbranched, smooth or verrucose, terete or flattened.Inflorescences axillary, racemose, few- to many-flowered.Flowers resupinate, small, usually white but sometimes tinged with pink, brown or green.Sepals and petals free, mostly erect or spreading; lip free, almost entire to rather obscurely three-lobed, spurred at the base.Column very short to elongate, androclinium excavated, anther terminal; rostellum lobes 2, short to very long, dependent to porrect; pollinia 2, sessile on single stipes; viscidium 1, variously shaped; stigma distinctly excavated below the rostellum, variously shaped.Ovary short or elongated.Capsule cylindrical, ellipsoid or ± globose, sessile or pedicellate.
Often leafless and epiphytic or rarely lithophytic herbs. Roots often dense, terete or less commonly dorsiventrally flattened, smooth or rarely verrucose, unbranched or with a few branches, usually elongate. Stem ‘woody’, terete, with acute to rostrate scale-leaves apically. Inflorescence axillary, racemose, concentrated in apical part of stem; rachis terete or angular, smooth or with processes; bracts sheathing or not. Flowers sessile or pedicellate, usually white variously tinged with green, brown or pink. Sepals and petals free, subsimilar. Labellum entire or obscurely trilobed, free, usually with fleshy calli at base on either side of spur mouth; spur globose, cylindrical or variously swollen. Column with a hemispherical anther cap, often elongated at apex, pollinia two, subglobose to pyriform, stipe (tegula) linear to oblanceolate, entire or bird-like at the column apex, viscidium linear or oblong; rostellum bifid after removal of pollinia, no longer than column.
Schill and Pfeiffer (1977) studied the pollen of M. exilis, M. guyoniana (Rchb.f) Summerh. (= M. globulosa), an unidentified species, and Solenangis aphylla (Thouars) Summerh. (now M. aphylla (Thouars) Summerh.). Sculpturing is laevigate. The sexine is calymmate, wavy, and about 0.3 μm thick. In his elegant monograph of the genus, Jonsson (1981) examined pollinium ontogeny with electron microscopy; he identified specialized viscin-secreting cells that degenerate at anthesis, leaving a cavity through which viscin threads connect to the pollinium to the tegula.
Gen. Sp. Orch. Pl.: 60 (1830); Summerh. in Bot. Mus. Leafl. Harv. Univ. 11: 140 (1943) & 250 (1945); L. Jonsson in Symb. Bot. Upsal. 23(4): 63 (1981)
Gen. Sp. Orchid. Pl.: 60 (1830). —Summerhayes in Bot. Mus. Leafl. [Harv. Univ.] 11: 140 (1943); 250 (1945). —L. Jonsson in Symb. Bot. Upsal. 23, 4: 63 (1981).
Gen. and Sp. Orch. Pl. 60 (1830).