The Members of a Lichen

In the laboratory, it is possible to tease apart the two members of a lichen, grow them independently in culture, and bring them back together again to re-establish the lichen. This, however, is strictly a laboratory feat. And while there may be a disassociation in nature that allows the alga to grow alone, the fungal component of a lichen does not survive alone in nature.

The fungal host is most commonly an ascomycete. In several species of lichen, however, it is a basidiomycete. When associated with algae as lichens, fungi are able to perform the perfect type of reproduction to produce asci or basidia. Attempts to bring this about in fungi that have been separated from their algal companions in the laboratory have not been successful, however.

Blue-green algae such as Croococcus, Gloeocapsu, and Nostoc often serve as symbionts in lichens. Among the green algae, Chlorococcum and Trebouxia often fulfill this role. Each lichen generally encompasses a single algal species; some, however, encompass two or even three.