Hypnum alaskae Kindberg; Stereodon callichrous (Bridel) Braithwaite

Plants medium-sized, pale green to yellow-green. Stems 2-6 cm, yellow or green, procumbent to ascending, regularly to irregularly pinnate, branches0.2-1 cm; hyalodermis present, central strand present; pseudoparaphyllia lanceolate. Stem leaves falcate to circinate-secund, ovate to ovate- lanceolate, , gradually narrowed to apex, 1.5-2 × 0.7-0.8 mm; base decurrent; margins plane, serrulate at apex; acumen slender; costa double and short or obscure; alar cells , region well defined, 1-3 cells high, ; basal laminal cells shorter, broader than medial cells, yellowish to green, walls porose; medial cells 50-60 × 8 µm. Sexual condition dioicous; . Seta red-brown, 2-3.5 cm. Capsule inclined, red-brown, cylindric, 1.5-2 mm; annulus 1- or 2-seriate; operculum conic; endostome cilia appendiculate.

Capsules mature Jun-Jul. Epiphytic or terrestrial, forests, open terrain; low to moderate elevations (0-1500 m); Greenland; Alta., B.C.; Alaska, Wash.; Europe; Asia.

In North America, Hypnum callichroum is frequent only near the Pacific Coast, where it is relatively easy to determine; the shiny plants produce sporophytes in summer. The alar cells are bounded by quadrate to triangular cells distally. The presence of a hyalodermis and the distinct alar region of thin-walled cells that are strongly differentiated from the adjacent cells are reliable characters. However, material without sporophytes can be difficult to determine. Epiphytic specimens frequently have sporophytes, while terrestrial ones generally lack them.