From the Greek 'selene’, a moon or crescent, and 'pedilon’, a sandal or slipper, in allusion to the incurved margins of the lip which are crescent-shaped if viewed from above. (Pridgeon et al., 1999).
WCM Protologue Reference:
Rchb.f., Xenia Orchid. 1: 8 (1854)
Tall terrestrial herbs. Roots elongate, fibrous, arising from a short to elongate rhizome; rhizomes present, short, creeping, rather fleshy. Stems erect, 2-5 m tall, often branching, rather woody, leafy, clustered or well spaced, terete, hairy, enclosed by sheathing sterile bracts below and leaf bases above, several-leaved; pseudobulbs absent. Leaves spreading or suberect, several-many, plicate, many-veined, elliptic-lanceolate to linear-lanceolate, acute or acuminate, green, glabrous or sparsely hairy, ciliate or not on the margins, contracted at the base to form a cylindrical sheath. Inflorescence terminal, racemose or branching from base, many-flowered; rachis terete, densely hairy; bracts usually leaf-like but much smaller than the uppermost leaf, lanceolate, hairy. Flowers with a persistent perianth, small to medium-sized, resupinate, concolorous or bicoloured; pedicel obscure to short, hairy; ovary trilocular, with parietal placentation, three-ribbed, hairy, crowned with a marcescent perianth. Sepals valvate. Dorsal sepal erect to hooded over lip, ovate or elliptic, obtuse or acute, pubescent on the outer surface, ciliate or not; lateral sepals usually fused to form a concave synsepal that is similar to the dorsal sepal, but free at the tips, pubescent on outer surface, ciliate or not. Petals free, spreading or incurved, lanceolate or linear-lanceolate, blunt, acute or acuminate, often pubescent in basal half within, not ciliate. Lip deeply pouched and inflated, slipper-shaped, glabrous on outer surface; side lobes obscure, incurved, entire; midlobe deeply saccate, calceiform or urceolate, incurved on front margin, hairy within especially on lower surface. Column porrect, short, stalked; anthers two, bilocular, borne on short obtuse filaments; pollen powdery or viscid; staminode terminal on column, more or less sessile or stalked, ovate or trullate, somewhat conduplicate, glabrous; stigma very short stalked, dependent, trisulcate, papillose or not, wider than the staminode. Capsule spreading to dependent, three-ribbed, cylindrical to fusiform, smelling of vanilla; seeds subglobose, crustose. (PC)