Definition of Ustilaginales
: an order of parasitic basidiomycetous fungi that cause smuts of various plants and especially of cereal grasses and have a complex life cycle which may include conidia production and in which sessile haploid basidiospores ultimately yield thick-walled dark-colored chlamydospores which typically replace the ovaries of an infected plant in a smutty mass and germinate with a meiosis to form a promycelium and begin a new basidial generation — compare uredinales , ustilago — see tilletiaceae
