Lichen: A Romance between Fungus and Algae

Biology / 8 min read / 11 August 2021

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Lazy Science Reader,

For a long time, we have been using something called a litmus paper. Red and blue, acidic – basic, ring a bell? But do we really know where does litmus paper come from? Does it magically rain from the sky? As much fun it would be to watch that, it sadly doesn’t. We obtain litmus paper from something called lichen. Of course, we all must have seen lichen almost everywhere, but we always ignored them and declared them to be moss. These organisms have something very special about them; they are not a single organism. Don’t get it? It’s okay, this article will tell you all you need to know about these fascinating microorganisms.

Let’s start with their history. Since a long long time, lichens as we know (or might not) were considered to be a type of plant species. It was in 1867 when a Swiss botanist Simon Schwendener stated that lichens were none other than a symbiotic relationship between fungi and algae or cyanobacteria. At that time, Schwendener did not provide any proof for his theory and adding to that was the belief of scientists that all organisms were autonomous. Schwendener's theory of a combination, or symbiotic relationship leading to the formation of lichen was rejected. Eugen Thomas was the one to perform further experiments and his results were published in 1939 on the dual nature of lichens. Other than these prominent figures who contributed in the evolution of lichens, Toby Spribille, who hailed from a Montana trailer park, collected 45000 samples of lichen throughout his career.

Now you know how lichens were completely discovered in bits and pieces by multiple people. Moving on, how does this symbiotic relationship work? As the name suggests, a symbiotic relationship is an all-beneficial relationship. We all know that algae contain chlorophyll. Due to the presence of chlorophyll, it can perform photosynthesis which fungi clearly cannot. Hence, algae produce carbohydrates which suffice as foods for fungus and in return the fungus provides strength, shelter and moisture to the algae. Lichen can be divided into three types: Fruticose, Crustose and Foliose. Structure wise, foliose lichen are coiled, leafy and they grow in layers. Crustose lichens are closely attached to the surface of rocks, soils or tree trucks with a distinct red, yellow or greyish-white color. Fruticose lichens are shrubby and are usually found hanging from trees.

When we ponder upon this, we do attain a lot of knowledge about lichens. However, how do they affect our surroundings? Lichen, when on rock surfaces release certain chemical substances which help in breakdown of rocks resulting in soil formation. Several dyes are extracted from lichen due to their distinct color when moist. Elaborately, a part of the sample lichen is taken and put in water to which ammonia is added (urine was used for this purpose before as it consists of 0.05% ammonia and 95% water). As stated in the beginning of this article, we also obtain litmus paper from lichens which help us categorize substances on their basis of their nature ie. Acidic or basic. Litmus is usually obtained from the lichen species namely Rosella tinctoria.

Now you know quite a lot about these organisms and can identify them with ease.


  • Beard Lichens are species of lichens which were burnt long ago to treat cough.
  • Body cavaties of mummies were filled with lichen during burial in Ancient Egypt.
  • Lichens are severely affected by sulfur dioxide. Sulfur dioxide hinders spore formation for reproduction.
  • Lichen can survive in almost every habitat ranging from tundra to tropical forests.
  • Crustose lichen are well known to combat against herbivory.
  • Caribou in an animal belonging to the deer family which mostly feeds on lichen during winter. Lichens are also used by birds for making their nests.