Lichens are a widely distributed organism that lives in symbiosis with algae. The symbiotic relationship is between fungus and algae acting as one organism. Lichinomycetes are a class of ascomycete fungi, which majority of lichens belong to. Trebouxia and Trentepohlia are the two most common photobionts.
The three most common growth forms of lichens are foliose, fruticose, and crustose.
Foliose: These are flattened and leaf like, having distinct upper and lower margins. Typically the upper margin contains the photosynthetic layer and reproductive structures. The lower surface may have rhizines or other structures that attach to the substrate. Most are stratified into 4 layers. The medulla, upper cortex, lower cortex, and the algal layer.
Fruticose: Shrubby and attached to substrate at a single point. Branches may be rounded or flattened. Resemble tiny trees or bushes. They are long thin, and have a round cross section. This one is stratified into the algal layer, medulla, and cortex. These do not contain a definite top or bottom.
Crustose: A Thin crust that grows on or in the substrate. It can not be detached. Can be areolate. Divided into an upper cortex, that protects the algal layer, which is in the medulla (beneath).
Lichens are so widely diverse and grow in all terrestrial and some aquatic, and marine habitats. As the environment becomes more extreme the role that lichens play in the ecosystem becomes more important. Lichens function like a photosynthetic plant and will often compete with plants of similar size. However they are biologically a symbiosis of a fungus and an alga or a nitrogen fixing cyanobacterium. They are stress tolerators for natural environment factors. Lichens lack a protective structure, therefore they can readily absorb environmental chemicals.
Human uses: Many lichens are used for making wool and fabric dyes, The lichen is cut into pieces and added to water. Ammonia is often added to the water. Other uses are deodorant, toothpaste, salves, and perfumes.
Lemon Lichen (Candelaria concolor)
A brightly colored lichen that grows on bark. It is a foliose, but can appear as a crustose because of its small lobes. the upper surface is typically yellowish and the bottom white.
Plitts Rock shield Lichen (Xanthoparmelia plitti)
Has bumpy pores, is gray in color and is commonly found on rocks. Plitti is a medium sized lichen but can form large patches.
Hooded sunburst (Xanthomendoza or Oxneria fallax)
A very small lichen that is yellow to orange in color. It is a foliose lichen that grows on bark and sometimes on rock. It does not grow in very dry areas and the thallus grows in rosettes to 3 cm in size.
Common Greenshield (Flavoparmelia caperata)
This lichen is medium sized and a foliose. Its coloring is a distinctive pale yellow green on the upper cortex when it is dry.
Common tree-skirt moss (Anomodon attenuatus)
The Common Tree-skirt moss is a perennial evergreen moss. the stems are light green. Individual stems can grow up to 3cm long. The leaves can grow anywhere from 1-2mm ling. The leaves are toothless in margin except near the tips.
Porella Liverwort ( Porella platyphylloidea)
The Porella liverwort is a sister o the Eurasian P. Platyphylla. Its leaves are shiny and a dark green. It has ovate lobes. The leaves are in opposite arrangement. This liverwort likes to grow in regions with a lot of moisture and not a lot of sunlight.