Subspecies 6 and 8 of T. pigmentosa (formerly syngens 6 and 8 of T. pyriformis) share a mating-type system controlled by three alleles with "peck-order" dominance at a single locus. The system is apparently closed and limited to three mating types that are homologous, but not identical, in the subspecies. These relationships are reflected in new mating-type designations.-The viability in some i...