horsehair lichen: any of several lichens of the genus Alectoria having a thallus consisting of filaments resembling hair
lichen: any thallophytic plant of the division Lichenes; occur as crusty patches or bushy growths on tree trunks or rocks or bare ground etc.
aspleniaceae: one of a number of families into which Polypodiaceae has been subdivided in some classification systems; includes genera Asplenium, Pleurosorus, Schaffneria