Deciduous perennials, terrestrial or epilithic, often succulent herbs (no shrubs in Thailand). Stems erect, glabrous or pubescent, with few nodes; new vegetative buds
produced from the rhizome during the dry season which then develop during the
rainy season. Leaves opposite and distichous, less commonly ternate, simple, few to many, usually in unequal pairs (anisophyllous), sometimes isophyllous, new vegetative leaves slightly whorled or tufted in close pairs; exstipulate. Leaf blades mostly subcoriaceous; asymmetrically ovate, lanceolate, elliptic-oblong, oblong, obovate, or orbicular; apex rounded, obtuse or acute; bases obliquely acute or rounded to shal-lowly cordate; margins variously serrate-dentate; upper surface sparsely to densely sericeous with multicellular hairs, rarely nearly glabrous; lower surface glabrous or pi-lose, sparsely covered with multicellular eglandular hairs; pigment glands, if present,
usually on the undersurface or sparsely so on other organs. Inorescence cymose, with few to many owers. Bracts free, paired, ovate, apex rounded; bases broad, margin
entire, caducous to persistent. Calyx mostly regular, less commonly irregular; tubular