Annual herbs, hygrophilous, glabrous. Stem ± quadrangular. Leaves opposite or whorled, rarely allernate. Inflorescence axillary, biparous cymes or glomerules. Flowers (4-)5-merous, subsessile or pedicellate, 2-bracteolate; bracteoles much shorter than flower. Hypanthium ± membranous in fruit. Epicalyx represented by mere folds, obscure or absent, rarely prominent. Petals 0-4, longer than sepals, caducous. Ovary globose, style absent or short. Capsule included or exceeding the hypanthium, globose, irregularly circum¬scissile.