M. plumula is a common but easily overlooked moss that may be found growing on rocks or epiphytically in wet forest to rainforest.

In sterile shoots the leaves are arranged in two ranks but on fertile shoots the leaves are arranged spirally and are overlapping. The leaves are usually asymmetric and have a single nerve which reaches about half or beyond the middle of the leaf.

Fertile specimens may be mistaken with Achrophyllum dentatum but the latter species is often much larger and the leaves have toothed margins. Rhizogonium distichum is also a similar but larger species with toothed leaf apices.