Cilia

Singular Cilium, Adjective Ciliate

An uncommon feature of Colorado Lichens, a trip to Eastern North America will yield many foliose species with cilia. Cilia are hair like structures at growing at the margins of a lichen. They could be mistaken for Rhizines, however rhizines serve to attach the lichen to a substrate and should be present on the lower surface of the lichen versus solely marginal.

At the time of writing this Physcia adscendens was the only lichen species in Colorado I had photographed with cilia. Park County, Colorado.
Very not from Colorado this Parmotrema sp. has more textbook looking cilia. Great Dismal Swamp, Virginia.
Cilia from above under microscope. Note that the cilia emerge right at the edge of the lichen between the upper and lower surfaces (marginal).