If you’re lucky enough to find this moss when it has capsules, there’s no mistaking it for anything else. Unfortunately, most of the time all you’ll find is patches of the gametophyte, looking anonymous on soil in a dark place, such as below the lip of a bank.
Fortunately, though, D. foliosum has a subtle but distinctive appearance that sets it apart from acrocarps of a similar size and habitat. If you look at dry plants, you’ll see how opaque and dull the leaves are. That’s because they are two or even three cells thick (except at the very base) and the cells are strongly mamillose, so they scatter the light. Also, the leaves are very strap-like, with a poorly defined nerve. Quite often, the plants are brownish too.Read the Field Guide account