Annual or perennial herbs with short underground root tubers or tuber-like rhizomes attached to roots of host plants. Stems simple or branched, often stout, with numerous scale lvs. Fls in dense spikes or racemes. Calyx either irregularly 4-(5)-toothed or laterally 2-lipped with usually 2 entire or 2-fid segments, sometimes with a fifth posterior tooth. Corolla strongly 2-lipped; tube curved; upper lip ± 2-lobed; lower lip 3-lobed, at least as long as upper. Stamens included. Ovary with 4 placentae, variously lobed. Stigma lobes fleshy. Valves of capsule sometimes remaining attached apically. Seeds minute, very numerous.