STUDY OF EXTERNAL FEATURES OF THALLUS (BASIDIOLICHENS)
- The basidiolichens are tropical in distribution and are found growing upon bare soil, rocks and trees.
- There are only three genera of basidiolichens and out of these Cora pavonia is the best known.
- The thallus is much lobed, internally attached to the substratum by rhizines and resembles superfically with ‘bracket fungi’.
STUDY OF INTERNAL STRUCTURE OF THALLUS (BASIDIOLICHENS)
- As seen in a vertical cut, the thallus is differentiated into three layers-the superior layer, the algal or gonidial layer and the inferior layer.
- The superior layer is uppermost and consists of loose felt of more or less perpendicular hyphae.
- The algal layer is the middle one. It is made of algal cells (Chroococcus species) intermixed with loose hyphae.
- The inferior layer is the lowermost which is a dense felt of hyphae running in all directions.
- The lowest surface bears concentric outgrowths of more or less perpendicular hyphae.
- Each outgrowth is known as sub-hymenium and its lower face bears a palisade-like layer of basidia.
- Each basidium bears four terminal sterigmata with basidiospores.
- Basidiospores are thus shed from the underside of the lichen. These on contact with alga form a lichen.