Additionally , some lichen species are tripartate , containing both a cyanobacterial and green algal symbiont .
All cyanobionts inhabiting lichens contain heterocysts to fix nitrogen , which can be distributed throughout the host in specific regions ( heteromerous ) or randomly throughout the thallus ( homoiomerous ) .
Some lichen species are tripartate , containing both a cyanobacterial and green algal symbiont .
All cyanobionts inhabiting lichens contain heterocysts to fix nitrogen , which can be distributed throughout the host in specific regions ( heteromerous ) or randomly throughout the thallus ( homoiomerous ) .