As a symbiosis between a fungus and a photosynthetic alga or cyanobacterium, lichens have particular challenges when it comes to reproduction and growing fully mature lichens out of tiny baby lichens. Many lichens have mastered this challenge by producing small thallus portions that already look like tiny lichens and, once dispersed, immediately start growing and forming a fully functional lichen. These tiny "greenhorn" lichens growing on their parent lichen are called phyllidia or lobules, due to their flattened appearance that resembles the lobes of mature lichens, only much smaller. Lichens can produce hundreds, if not thousands of these "baby" lichens, but only very few survive in nature.
Here is a selection of examples of such "greenhorn" lichens, that is, lichens with tiny phyllidia or lobules growing on parent lichens, ready to be dispersed and begin a new life as separate individual: Pseudocyphellaria multifida, P. glabra, P. dissimilis, and Sticta filix.