Fungi are divided into four-classes according to the septation of mycelium and on the basis of characteristic features of reproduction; Ascomycetes, Phycomycetes, Deuteromycetes and Basidiomycetes. Phizopus belongs to Phycomycetes. It is also known as water mould. Penicillium belongs to class-Ascomycetes. It is also known as sac fungi. Ustilago is a member of Basidiomycetes. It is known as club fungi. Alternaria belongs to Deuteromycetes (fungi imperfecti).