One of several widespread species with round, obliquely inserted leaves, Nardia scalaris is very common in the uplands but is sadly all but absent from the southern lowlands. Unlike its aquatic sister, N. compressa, this plant likes damp but not very wet habitats such as track and stream banks in high rainfall areas. Confusion is easily possible with the very common Solenostoma gracillimum which also has round leaves and lives in similarly disturbed places.
You’ll need to use your hand-lens to look for the tell-tale spreading underleaves of N. scalaris. They are narrow and peg-like and if you examine a shoot from the side, they usually stick out in profile (there are some good images below). On older parts of the stem they often get obscured by rhizoids so make sure to check for them near the shoot tips. If they are not present then you are more likely to have S. gracillimum.Read the Field Guide account