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