Shrubs or trees. Trunk often fluted. Branches unarmed, with fissured bark, not lenticellate. Leaves opposite, ternate, quaternate, or in some lateral branches occasionally alternate, petiolate (or only in N.gracilis often sessile). Inflorescence terminal, thyrsoid, but often dichotomously branched. Ultimate branches topped by solitary flowers or by heads of three or more flowers which may be globose. Lower bracts mostly leafy, the others small, often scale–like. Flowers 4–merous, actinomorphic except for the more or less irregularly lobed calyx. Calyx campanulate to cylindrical, 4–lobed; lobes much shorter than the tube, triangular, acute or rarely obtuse or rounded, entire or sometimes tridenate (only observed in N. floribunda and N. gracilis), erect or suberect, sometimes two or two pairs coherent or partially united; flowers with almost regularly 4–lobed calyx or the irregularly lobed calyx in a single inflorescence, with minute glandular hairs and often also simple or branched hairs; inner side mostly sericeous to appressed–pubescent. Corolla mostly white or creamy, circumscissile, outside with some minute glandular hairs at the base of the lobes and the apex of the tube; inside with a pilose or villose ring of mostly recurved hairs in the throat and with minute glandular hairs in the tube except for its glabrous base (hairs in corolla throat or in tube may be absent on a few occasions, but in those cases never both kinds simultaneously); tube slightly shorter or less often longer than the calyx, cylindrical; lobes oblong, recurved from above the base and there convex and often with a minute callosity, concave and rounded to acute at the apex, entire. Stamens well exserted, inserted at the mouth of the corolla tube; filaments only at the very base vilose in a line with the group of hairs on the corolla throat or slightly above or entirely glabrous, straight or curved, geniculate at the base only in N. floribunda; anthers glabrous, 0–5–2 mm. long; cells 2, parallel when young, conspicuously divergent after the pollen has been shed, confluent at the apex, dehiscent throughout by a longitudinal slit. Pistil: ovary superior, obcordoid, ovoid, or ellipsoid, mostly slightly laterally compressed, appressedly pubescent or hirto–pubescent, glabrous only in N. floribunda, at the very base, however, always glabrous, surrounded by a narrow disk–like ring formed by the base of the shed corolla, 2–celled; style well exserted, glabrous; stigma small, capitate or occasionally slightly bilobed. In each cell one axile peltate placenta with many ovules attached to the middle of the septum. Capsule about as long as and included in the persisting calyx or up to about one–third longer, with about the same indumentum as the ovary, bivalved, septicidal, retuse or rounded at the apex; often later longitudinally cleft, the capsule becoming 4–valved. Seeds small, medium brown, fusiform, longitudinally striate or reticulate–striate.