What They Are. These fascinating plants are actually the result of algae and fungi working together to survive. Many different types of lichens can be seen around our city trees, generally on the trunk and branches.It’s not uncommon to see several varieties of lichens on one host tree, either in small clusters or flaky patches.hat They Are. These fascinating plants are actually the result of algae and fungi working together to survive. Many different types of lichens can be seen around our city trees, generally on the trunk and branches.