Hylocomiastrum Brotherus in H. G. A. Engler and K. Prantl, Nat. Pflanzenfam. ed. 2. 11: 486. 1925.
[Hylocomium, a related genus, and Latin -astrum, incomplete resemblance]
J. R. Rohrer
Plants prostrate with ascending-arching innovations; growth sympodial. Stems remotely and irregularly pinnate to regularly 1--2-pinnate; paraphyllia dense, highly divided from a multiseriate base into 1--2-seriate branches. Stem leaves often remote, erect-spreading to spreading, broadly ovate, ovate-deltoid, or ovate, strongly plicate, not rugose, not to somewhat decurrent; margins spinose-serrate to serrate in distal two-thirds, serrulate to nearly entire at base; apex acute to acuminate; costa single, double, or rarely triple, sometimes branching, extending 1/3--3/4 leaf length, sometimes ending in a sharp spine; cells smooth; alar cells not differentiated. Branch leaves broadly ovate to ovate-lanceolate, apex acute to acuminate; costa extending 1/2--3/4 leaf length, spinose. Capsule inclined to horizontal; operculum conic; exostome teeth irregularly cross-striolate to somewhat reticulate proximally on exterior surface; endostome segments with narrow perforations along keel.
Species 3 (2 in the flora): cool-temperate and boreal regions, North America, Eurasia, n Africa.
Proximal leaves of stems and branches are distinctly shorter than the others and have nearly entire margins, acute to bluntly apiculate apices, and weaker costa. Hylocomiastrum differs from Hylocomium, with which it is often combined, in its shorter-branched paraphyllia, strongly plicate leaves, strong costa that are often single and end in a spine, smooth leaf cells, endostome segments with narrow perforations, and conic-apiculate opercula.
