The next image is the cross section of the basal part showing an oval lumen. . Dark blue round to elongated elements are of fungal cells and hyphae, and rather large, round and greenish coloured structures are of algae spread in the body of this lichen. The lower surface of lichens may be pigmented. These pigments have long been used as natural dyes. Algal cells contain chlorophyll to catch the sunlight and to perform photosynthesis using CO 2 and water.
Fungal cells provide the housing for algae and receive foodstuff in return from the algae.
UMAR Fungi in lichens belong almost exclusively to the Ascomycetes. They form asci, which are specialized cells producing their spores, and also cup shaped structures. UMAR Algae as symbiont in lichen, and thread-like hyphae of the fungus. . UMAR The relatively thick wall of the lichen may give rise to new lichen formations by producing internal or superficial nodules, microscopical caricatures of the main lichen body, as illustrated below. Fungal symbionts produce ascospores but they do not initiate independent new growth.