Lichen Identification

How are lichen species identified?

The classification of lichen, like that of fungi, are undergoing constant change. 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. Most lichens are considered to be edible (or at least not poisonous). If not disturbed they can live for centuries.

Identification Characteristics

Thallus characters: Growth form, size, shape of the thallus, colour of cortex, rhizines and cilia of the lower cortex and margin, pores and cracks of the upper cortex. Reproductive characters: Presence of vegetative propagules; shape and colour of the apothecia (if present), shape, number of cells, size, colour of the ascospores. Chemical characters: Production of lichen compounds. Ecological characters: Distribution, elevation, habitat, substrate. Algal host: The type of alga, either chlorophyta or cyanobacteria.

Crustose Form

What are the lichen growth forms? Lichens can be divided into three basic forms depending on the form of the thallus. Crustose: Crust-like, adhering tightly to the substrate by their entire lower surface. Some endolithic lichens are embedded in their rock substrate. Foliose: Leaf-like with a distinct upper and lower surface which are attached to their substrate only by small root-like structures (rhizines) Fruticose: Shrub-like, pendulous strands or hollow stalks called podetia, usually attached to the substrate at the base or holdfast.

Foliose Form Fruticose Form

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