Polytrichaceae. Genus Psilopilum

1. Leaves ovate; leaf margins serrulate above, below with distinct border of thin-walled cells; lamellae 8-15, coarsely and irregularly dentate in profile 1. P. laevigatum
Rather widespread species in the Arctic and Siberian Subarctic. Confusion with the superficially similar P. cavifolium and Oligotrichum falcatum can be avoided by examining the marginal border, which is always conspicuous in this species.
Leaves oblong-ovate; leaf margins entire above, below without or with moderately distinct border of thick-walled cells; lamellae 5-10, entire or minutely crenulate in profile 2. P. cavifolium
Widespread species in the Arctic and Subarctic, but more common in East Siberia. Most reliable difference from previous species is the subentire upper edge of lamellae.