Highly resolved spectra are presented which show how the low-magnetic-field energy-level structure of a single-electron atom gives rise to the quasi-Landau resonances as the field is increased. Data from the strong-mixing region where electric and magnetic forces are comparable reveal that evenly spaced energy levels are a general feature, irrespective of parity and magnetic quantum number of the states. The quasi-Landau resonances emerge by a concentration of oscillator strength into a single level of each term.