The river jelly lichen (Collema dichotomum) is found on flat sandstone rocks on the east bank of the River Isla above Bridge of Dillavaird. This aquatic lichen grows on submerged rocks in partial shade in cool, clean and fast-flowing intermediate and upland streams. The dry lichen is very brittle but turns into a jelly like texture when wet. It is rare in the UK and has been declining since 1960, and is now known only from eleven 10 km squares in mid-Wales, northern England, Scotland and Northern Ireland. Its distribution also extends into northern Europe and Russia. River jelly lichen is regionally threatened, listed as vulnerable on both the IUCN/WCMC and GB Red Lists, and is protected under Schedule 8 of the Wildlife and Countryside Act 1981.