Species with combinational dormancy have more than one type of dormancy. These seeds have physical plus physiological dormancy.
Each dormancy condition must be satisfied in sequence to get the seeds to germinate.
For example, Eastern redbud (Cercis canadensis) seeds must be scarified to start imbibition followed by about 6 weeks chilling stratification before they will germinate.
Germination in Eastern redbud (Cercis canadensis).