The irreducible-spherical-tensor form of the effective-mass Hamiltonians for acceptors in cubic semiconductors in a homogeneous magnetic field parallel to a (001) direction or to a ( 111) direction has been derived. The Hamiltonians take into account the full structure of the I g SI 7+ valence-band edge, and they contain a point-charge potential with spherically symmetric qdependent dielectric screening. The eigenstates have been calculated variationally for the case of acceptors in germanium. For both orientations, the computations have been performed as a function of the magnetic-field strength, in the range from 0 to 5 T. The binding energies of the first 36 odd-parity excited states and of the first 4 even-parity states (which form the ground-state multiplet) are obtained. The oscillator strengths of the electric-dipole transitions from the ground-state sublevels to the excited states are also calculated, and the results are used to simulate theoretical acceptor excitation spectra, which are in excellent agreement with the available experimental farinfrared-absorption and photothermal-ionization-spectroscopy spectra. For the ground state and for the final states of the G and D lines, theoretical g factors are obtained which are very close to the experimental ones. In particular, the values g& = -0.45 and gz =+0.22 are computed for the acceptor ground state. It is found also that for the ground state and for the excited I 8( Td ) final states of the G, D, and B spectral lines, the ratio r =g2/4g& is always very close to the special value --', , which corresponds to a linear Zeeman splitting of the I 8 states into a degenerate doublet for B~~( 111)and into an equally spaced quartet for B~~(001 ).