Mosses are defined as simple plants with the most basic of root structures, leaves, and stems. Lichens are a very different type of creature, called a composite organism. Not just a plant, lichens are actually a single entity created from a joining of algae and fungus.
http://knowledgenuts.com/2014/01/13/the-difference-between-moss-and-lichen/
These two types of lichen clearly lack any kind of leaf-like structure and are more closely likened to the appearance of rust or other grainy crust. Because the leaves and stems of mosses can be tiny, it can be difficult to tell the difference at a glance.
http://knowledgenuts.com/2014/01/13/the-difference-between-moss-and-lichen/
Most mosses have narrow, elongated leaves, and they can come in as wide a variety of colors as lichens. Some mosses have leaves that are so tiny that a magnifying glass might be needed to tell whether or not the growth is made up of leaves and narrow, tiny stems or leaf-like fungal structures. Some moss species grow to only a millimeter or so in height. Both moss and lichens can be found in almost every area of the world. Lichens can be found in even the coldest of Arctic climates; they are an important part of the environment’s nitrogen cycle, and are as commonly used as as food source as moss is.
http://knowledgenuts.com/2014/01/13/the-difference-between-moss-and-lichen/
Lichens can absorb minerals and water straight through their thalli and can concentrate minerals even when there are only trace amounts in the air. If one of the entities begins to grow faster then the other entity, the lichen will fall apart (Brodo, 3-8).
http://www.amnh.org/learn-teach/young-naturalist-awards/winning-essays2/2007-winning-essays/lichens-as-indicators-of-vehicle-pollution/
A lichen is not a single organism. Rather, it is a symbiosis between different organisms-a fungus and an alga or cyanobacterium. Cyanobacteria are sometimes still referred to as 'blue-green algae', though they are quite distinct from the algae. The non-fungal partner contains chlorophyll and is called the photobiont. The fungal partner may be referred to as the mycobiont. While most lichen partnerships consist of one mycobiont and one photobiont, that's not universal for there are lichens with more than one photobiont partner.
https://www.anbg.gov.au/lichen/what-is-lichen.html
The formula for the IndVal is simple; using the data from Charts 1, 2, and 3, the mean number of lichen species in a zone is found by adding species values and dividing by the number of stations in that zone. The species values range from 0 to 3, and the number of stations was always six.
http://www.amnh.org/learn-teach/young-naturalist-awards/winning-essays2/2007-winning-essays/lichens-as-indicators-of-vehicle-pollution/
Interface dermatitis A method based on epidermal changes Philip E. LeBoit, M.D. Depts. of Pathology and Dermatology University of California, San Francisco I. Introduction An inflammatory skin disease in which the junction between the papillary dermis and epidermis is obscured is termed an interface dermatitis.
http://www.dermatology.ucsf.edu/pdf/interface%20dermatitis%20revised.09-10.pdf
You find this sort of structure in many foliose lichens. The thallus of Paraparmelia lithophiloides has an upper cortex and a lower cortex and that is the norm in foliose lichens. On the other hand, a crustose lichen lacks a lower cortex. It is meaningless to talk of upper and lower sides in the branches of a fruticose lichen.
https://www.anbg.gov.au/lichen/what-is-lichen.html
C. Lichen striatus 1. Definition Lichen striatus is a condition of unknown cause in which scaly papules due to an interface dermatitis with distinctive features occur in a linear distribution, generally following Blaschko's lines.
http://www.dermatology.ucsf.edu/pdf/interface%20dermatitis%20revised.09-10.pdf
Introduction: Lichens as Pollution Monitors. Lichens are not one entity but two, a symbiotic relationship between a fungus and algae. Photosynthesis and respiration only happen when the lichen absorbs water; the lichen is in a dormant state when dry.
http://www.amnh.org/learn-teach/young-naturalist-awards/winning-essays2/2007-winning-essays/lichens-as-indicators-of-vehicle-pollution/
what kind of entity is a lichen?
Lichens are not one entity but two, a symbiotic relationship between a fungus and algae.