Data from: Another Fennoscandian Tortella species with fragile leaves, Tortella fragmenta (Pottiaceae, Bryophyta)

The well-known limestone species Tortella fragilis consists of two
species, which are clearly circumscribed by the nuclear molecular marker
ITS, and the plastid atpB-rbcL and rps4. The morphological differences
between the two are relatively small. Because all specimens cannot be
identified with certainty they could be understood as semi-cryptic. The
two differ in the orientation of dry leaves and the appearance of papillae
on lamina cells in mid-leaf. Dry leaves of T. fragilis s.str. are often
screwed or slightly so, and near the shoot apex numerous leaves are
sometimes tightly adhering (or parallel) to each other and together
slightly screwed, or sometimes more loosely so or somewhat curled, and the
lamina cells are densely papillose with papillae that are difficult to
distinguish individually and obscure the cell walls. In T. fragmenta,
which is described as new, the leaves are at most slightly screwed,
curled, also near shoot apex, and not or hardly adhering to each other,
and the lamina cells are moderately densely papillose with distinct and
sometimes forked papillae that do not obscure the cell walls. Tortella
fragilis is widespread in Fennoscandia, whereas T. fragmenta occurs
primarily in the mountain range, with scattered occurrences in the
lowlands of the boreal zone. Both species occur in calcareous or base-rich
sites, with a tendency for T. fragilis to grow in wetter sites than T.
fragmenta.