Notes This alga is extremely resistant to desiccation and wave exposure, forming a dense, deep-red crust on the rocks. The holdfast is the lower layer of the crust. The colour is brick red to dull crimson and the texture is cartilagenous. It can resemble a patch of tar on the rocks.
It appears to have a high light requirement, and does not grow much lower than mid-tide level.
It produces its own food through the process of photosynthesis.