Lecidea laboriosa

Lecidea laboriosa is a species of lichen that grows inside solid rock (endolithic), with only the small black disc-like fruiting bodies (apothecia) visible above the rock surface.: 301  Unlike other members of the genus Lecidea, the apothecia are not lecideine in that they either lack black margins (exciples) or have gray vertically striated margins.: 301  It grows all over the world in all climates. It might be the most common endolithic lichen in California.: 301  It is similar in appearance to Catillaria lenticularis, Polyspora simplex, and Sarcogyne clavus.: 301  It is negative to lichen spot tests, K−, P−, C−.: 301 ...read more on Wikipedia.