Collema

Collema cristatum

Collema or Leimflechten is a genus of lichen- forming ascomycetes. Worldwide 80 species are known, of which 25 grow in Germany.

Description

Collema species are dark brown to black leaves lichens. In the dry state, the bearings are brittle, but swell considerably when wet and are then of gelatinous consistency. As photobiont occur cyanobacteria of the genus Nostoc on. If apothecia ( fruiting bodies ) may occur, these are red to dark brown, usually recessed fitting, edged discs. Many species are usually sterile and form isidia from serving the vegetative propagation. The lichens are rarely fixed with Haftern with rhizines the substrate.

Location

The species represented in Central Europe growing on tree bark, earth and rock. The epiphytic species live on deciduous trees with subneutraler bark, partly in warm, mild winter layers. Part also humid, oceanic most pronounced, rainy mountain areas are populated.

Gesteinsbewohnende Collema species typically colonize open light (often sunny ) locations that some time sickerfeucht remain after rainfall. Under these conditions, colonize about Collema callopismum, Collema cristatum, Collema fuscovirens, Collema multipartum and Collema Polycarpon also limestone rocks.

Endangering

All species are growing on bark sometimes threatened with extinction, partly already extinct. This apparently is due to a particularly low resistance to sulfur dioxide and a reduction in pH of precipitation water. Only Collema flaccidum that grows on siliceous rock, not responding so extreme.