Collema dichotomum (river jelly lichen)

Collema dichotomum, the river jelly lichen is rare amphibious fungus growing on siliceous rocks in cool and clean streams.

The dry lichen is very brittle but turns into a jelly like texture when wet.

Collema dichotomum demands on its environment make it an indicator of the ecological health of streams. Many European populations of this lichen have declined and it is confronted with threats from multiple sources.

Species detail

The river jelly lichen produces

small rosettes up to 2.5cm in diameter
Thalli are
- greyish dark green to almost brownish when dry
- dark to bright green (sometimes with a brownish tinge) when wet
more or less dichotomous branching pattern
convex lobes with the disc-like reddish brown fruiting bodies (apothecia) on the upper surface of the thalllus

Taxonomy

Find out about the appearance and structure of the river jelly lichen in comparison with other jelly lichen species. Learn the basionym and synonyms for this species.
Distribution and habitat

Discover where the river jelly lichen is found and the types of habitat it typically grows in.
Biology

Learn about the need for Collema dichotomum to have a compatible algal partner and find out why poorly developed apothecia, common in the southern range of the species, is raising concern.
Conservation

Populations of the river jelly lichen have declined in many parts of its European distribution range. Discover the current and potential threats to the survival of this species and find out what can be done to contirbute to a better understanding of its distribution.
References

Get reference material for Collema dichotomum.