sentences:  This is a useful tool for delimiting between the subdivisions.The Ustilaginomycetina has the type B secondary structure and they share this character with the Agaricomycotina, and it separates them from the Pucciniomycotina which has the type A secondary structure.In 1847 Tulasne and Tulasne divided the so-called smut fungi into two groups called Ustilaginacceae and Tilletiaceae.