Genus PtilidiumGenus PTILIDIUM, Nees
The species of the Genus Ptilidium grow usually in dense and brownish mats, the stems prostrate or ascending, 1 to 2 pinnate or irregularly and sparingly branched, without whip-like branches, the branches are lateral; root-hairs are few and short.
The leaves are obliquely inserted, variously cut or fringed, a character which suggested the name Ptilidium, derived from the Greek; down, the dorsal segment larger and with its tip lying over the base of the leaf next above it (incubus), underleaves (amphigastra) similar but much smaller.
Male flowers (antheridia) short-stalked in the axils of more closely imbricate leaves.
Female flowers (archegonia) terminal, sometimes apparently lateral because a side branch has grown on beyond the stem which bears it. Bracts commonly two pairs, similar to the leaves.
Perianth free, several times longer than the bracts, cylindrical egg-shaped with constricted mouth.
Veil (calyptra) free.
Spore-case egg-shaped on a moderately long stalk (seta) de
hiscing to the base by four rather rigid valves; spores dotted.
Elaters two to three spiral.
There are about eight species.
Ptilidium Ciliare Lichen