Gymnostomum Calcareum MossHabit and habitat.-Densely tufted, bright-green above, rusty below ; on shaded limestone rocks.
Name.-From calcarius, pertaining to lime, a name suggested by the plant's habit of depositing lime.
Plants (gametophyte). -Stems 1/4 to 3/4 of an inch long, covered with rootlets.
Leaves.-The lower very small, gradually or abruptly larger upward ; slender lance-shaped ; apex blunt ; vein extending to near the apex ; margin minutely blunt-toothed.
Habit of flowering.-Male and female flowers on separate plants (dioicous).
Veil (calyptra).-Split up one side.
Spore-case.-Exserted, oblong, yellow-brown, slightly constricted under the mouth when dry.
Pedicel.- 1/6 to 2/6 of an inch long.
Lid (operculum).-Base conical ; beak awl-like.
Annulus.-Short and persistent.
Spores.-Rare, mature in summer.