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Cyanobacteria General characters: Also called as Blue-green algae. Found in water and other wet places. These are oxygenic photosynthetic, prokaryotic and gram negative bacteria. The outer layer of cell wall is made of lipo-polysaccharides and inner layer is having peptidoglycon. Ribosomes, thylakoids and phycobilosomes are present in cytoplasm. Ribosomes are 70s type, thylakoids contains phycobilosomes which has photosynthetic pigments like phycocyanin, phycoerythrin and small amount of protein. Reserve food material is cyanophycin granules, starch, glycogen, phosphate granules. Gas filled vacoules helps the bacteria to float on the surface of water.  Vegetative reproduction is by fission, fragmentation and by locomotion harmagonia. Asexual reproduction is byformation of akinites, endospores, exospores and nanocytes. Thallus organisation in cyanobacteria: Thallus organisation in the sense no differntiation of organism into different parts. It is in  three forms.

Lichens: The symbiotic assosiation between fungi and algae resulting in a plant body is called lichens. Plant body of lichen thallus is irregular and made up of algal component i.e. phycobiont and fungal component i,e. Mycobiont. Differnt forms of lichens: 1. Crustose lichen:     These are flat, thin, crust like thallus appeared partly or completely embedded into the substratum.  Ex. Rhizocarpa graphis. 2. Foliase lichens:    These are flat, leaf like lobed thallus attach to the substratum with the help of rhizoids.  Ex. Permeria. 3. Fruticose lichens:     These are brush like hanging cylindrical or spherical shape. Attached to substratum with the help of basal mucilage disk.      Ex. Cladonia. Internal morphology of lichen thallus:    It shows mainly four zones. They are:            1. Upper cortical zone            2. Algal zone            3. Medullary zone            4. Lower cortical zone 1. Upper cortical zone:           It is a protective