Habitat
Polytrichastrum alpinum can be found on soil banks, in cliff crevices, on overturned tree roots, rotten logs, and on floors of coniferous forests.
Gametophyte
Overall structure:
This species is an acrocarpous moss. It forms loose, dark green turfs that attach to the substratum by rhizoids at the base of its shoots.
A distinguishing feature of this species is the reduced leaves near the base of the stems.
Leaf structure:
The leaves of Polytrichastrum alpinum are linear-lanceolate shape, with abruptly broadened bases that sheathe the stem.
The upper margins of the leaves are toothed, as seen from this ventral view of a leaf. The lamellae are visible as parallel longitudinal lines occupying much the lamina surface.
A leaf cross section provides another view of the lamellae.
The marginal cells of the lamellae in Polytrichastrum alpinum are papillose.
Male Gametophyte:
Pictured here are male gametophytes with antheridial splash cups which aid in the dispersal of sperm.
Sporophyte
Sporangium:
The sporangia of Polytrichastrum alpinum are pale green when young and turn brown with age. They are long, cylindrical, erect and often slightly curved. They are rounded in cross-section. Note the presence of a hairy calyptra on the young sporangium.
Seta:
The seta can be quite long and is light brown to straw-colored when it reaches maturity.