Collema dichotomum. River jelly-lichen.

Life-form & Growth Form:  

Perennial, branched fronds and rather seaweed-like, attaching to substrate at base. Branches strap-like and fanning out somewhat near their tips. Grows in colonies.  

Flowering period: 



 On generally base-rich, siliceous rocks in the middle reaches of rivers. The only Collema sp. which occurs in more or less permanently submerged habitats.


Sensitive to eutrophication but tolerant of moderate silting. Deterioration of water and air quality, water acidification and increased tannin levels as a result of afforestation. Reduced water levels. Deforestation causing increased silt loads in water and reduction in shade causing light shock. Competitive species such as Ivy outcompeting C. dichotomum on sections of riverbank.

Static distribution map:
Collema dichotomum
Collema dichotomum