Crustose lichen forms a thin crust adhering closely to the substratum. In some cases, this crust may be thick and lumpy, and may be detached, in part, or submerged below its surface. The thallus of a crustose lichen is usually only discernible because of the discolouration of the substrate.
Foliose lichen is one of a variety of lichens, which are complex organisms that arise from the symbiotic relationship between fungi and a photosynthetic partner, typically algae. This partnership allows lichen to live in diverse climates that can range from cold, dry mountains to wet, warm valleys.
A fruticose lichen is a form of lichen fungi that is characterized by a coral-like shrubby or bushy growth structure. It is composed of a thallus and a holdfast. It is formed from a symbiotic relationship of a photobiont such as cyanobacteria and two mycobionts.
fruticose - free-standing branching tubes. Despite the wide diversity of the basic growth forms, all lichens have a similar internal morphology. The bulk of the lichen's body is formed from filaments of the fungal partner, and the relative density of these filaments defines the layers within the lichen.
A squamulose lichen is a lichen that is composed of small, often overlapping "scales" called squamules. If they are raised from the substrate and appear leafy, the lichen may appear to be a foliose lichen, but the underside does not have a "skin" , as foliose lichens do.