Identification notes
Although it may not look like it at first glance, Atrichum undulatum is in the Polytrichaceae, whose members have leaves with ridges of tissue (lamellae) overlying the nerve and a drum-like membrane across the mouth of the capsule. In Atrichum, the nerve is narrow and therefore only has a small number of lamellae, which can be seen as parallel dark lines running along its upper surface (see photographs).
Well-grown A. undulatum is recognised also by its transversely undulate leaves, but poorly grown or young plants may lack these and then a cross section of the nerve will be needed to separate it from smaller Atrichum species. Beginners may confuse non-fruiting Mnium hornum with this plant but that lacks lamellae and leaf undulations.
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