  Luminosity Functions have been obtained for very faint dwarf galaxies in the
cores of four rich clusters of galaxies (Abell 2052, 2107, 2199 and 2666). It
is found that the luminosity function of dwarf galaxies rises very steeply in
these clusters, with a power-law slope of \alpha -2.2 (down to absolute
limiting magnitudes M_I = -13 and M_B = -11 for H_0 = 75 km/s/Mpc). A
steepening of the luminosity function at faint magnitudes may in fact be a
common feature of both cluster and field populations. Such a result may explain
the observed excess counts of faint, intermediate redshift galaxies in the
Universe, without resorting to more exotic phenomena. An alternate explanation
is that star formation in dwarf galaxies is less affected by gas loss in the
richest clusters, because of the dense, hot intracluster medium found in such
environments.
