No mushroom type structure is formed. The true mosses belong to the phylum Broyophyta. This phylum is unique because the gametophyte phase is dominant. They have no conducting tissue, so take in water and minerals directly from the environment through there leaves and stems. For this reason they must remain small and close to the ground.
Ground cover is one ecologically significant function of the true mosses.
Sphagnum moss, a true moss, is extremely absorbent. It also makes bogs very acidic due to a hydrogen pump it employs to balance its internal pH. Lichen Lichen is composed of fungi and algae. They live together in close association, and their relationship is categorized as a controlled parasitism. The fungus benefits because it receives sugars from the algae. The fungi cannot exist without the algae, however the algae can live independently.