The string fen at Newdegate Pass, Mt. Field, Tasmania consists of dams composed of bolster heath and peat derived from bolster heath, and flark ponds with concave sides and usually rocky floors. The bolster heath has a smooth surface which consists of a complex mosaic dominated byDonatia novae-zelandiae, Carpha rodwayi andDracophyllum minimum. The floors of the ponds usually support no macrophytes. The ponds situated on strong flow lines have shallower dams which are more often breached than those where flow is more diffuse. The ponds ultimately drain by tunnelling through the humified peat below the live roots of the bolster heath, and the exposed floors are colonized by bolster heath species. The underlying block stream has a topography partly independent from that of the string and flark features, which shift in both time and space.