  We report measurements of the effective $g$ factor of low-density
two-dimensional holes in a Ge quantum well. Using the temperature dependence of
the Shubnikov-de Haas oscillations, we extract the effective $g$ factor in a
magnetic field perpendicular to the sample surface. Very large values of the
effective $g$ factor, ranging from $\sim13$ to $\sim28$, are observed in the
density range of $1.4\times10^{10}$ cm$^{-2}$ to $1.4\times10^{11}$ cm$^{-2}$.
When the magnetic field is oriented parallel to the sample surface, the
effective $g$ factor is obtained from a protrusion in the magneto-resistance
data that signifies full spin polarization. In the latter orientation, a small
effective $g$ factor, $\sim1.3-1.4$, is measured in the density range of
$1.5\times10^{10}$ cm$^{-2}$ to $2\times10^{10}$ cm$^{-2}$. This very strong
anisotropy is consistent with theoretical predictions and previous measurements
in other 2D hole systems, such as InGaAs and GaSb.
