(C+red.) There are three basic chemical tests that may or may not yield a color change when applied to a lichen. … The color of the lichen body, known as a thallus, is very important for identification. James, P. W. (2003). The most conspicuous species of lichens on trees tend to be gray-green or yellow-green in color, but some may be orange, bright yellow, brown, slate blue, or black. There are about 15,000 described lichens which range in size from 1 mm to more then 3 meters, and come in many different colours and shapes. Aide Memoire: Usnea. It grows only on constant surfaces and is never seen on changing substrates like riverbeds, stones or unconsolidated earth banks. The classification of lichen, like that of fungi, are undergoing constant change. Test with potassium hydroxide dark green (K+green). Published by the British Lichen Society and is essential for anyone undertaking the identification of species in this genus. Lichen Identification: How are lichen species identified? Identification doubt because test with calcium hypochlorite positive red. Identification of crustose lichens is very challenging even with extant specimens, and often without precise information on anatomy (e.g. Lichenologist 29: 301-332. A Key to Sterile, Crustose, Saxicolous and Terricolous lichens of the British Isles. Two of these tests have been used for over 100 years. Fryday, A. and Coppins, B. J. The growth and the structure of the lichen mainly depend on the environmental conditions and climate. The gold dust crustose lichens of the Chrysothrix genus, such as C. xanthina shown here, are easily identified by their bright color. (Photo by Stephen Sharnoff, sharnoffphotos.com) Though lichens appear varied, they mostly adhere to the same basic structure. One method used for identification in lichens consists of some simple spot tests. Feb. 21, 2009 This warty crustose lichen grew on the bark of a maple tree at Tremont. Crustose lichen grows at a very slow rate compared to others. Baeomyces rufus Baeomyces rufus on North facing partially sheltered stone dyke. (xxxx). As a result, many species have been based solely on their chemistry since the end of the nineteenth century. 2012: 14: Smoky Eye Boulder Lichen Porpidia albocaerulescens Great Smoky Mountains NP Feb. 21, 2009 This is a very common crustose lichen that grows on the rocks in the park.