Mushroom Tree

 Mushroom trees and other giant forms of fungi, are mainly found on worlds with low gravity and dense atmosphere. They usually grow where it's damp and shady, such as under the canopy of huge trees in rain forests, but they can also be found in e.g. lava tunnels, and there are similar organisms which are adapted to arid and even sunny environments. Some mushroom trees have the feature of photosynthesis, either through symbiosis with micro-plants, or through endogenous photosynthetic pigments.