The Dorset heaths can be very dry in parts and elsewhere they can be very boggy with many other variations in between. Where the soil is peaty and quite wet one can find this delicate plant; bog pimpernel (Anagallis tenella).
It is related to the familiar scarlet pimpernel, a much more common weed of fields and gardens. Bog pimpernel is not rare as such but can only be found in suitable moist conditions and so may not be encountered very often. Where it does occur it can produce quite large carpets of leaves with these little flower heads appearing from amongst the leaves on stalks.
This is a member of the primrose (primula) family which usually have five petals this bog pimpernel I have photographed has seven!