  From a combination of deep Hubble Space Telescope V and I images with
groundbased images in the same bands, we have obtained color-magnitude diagrams
of M10, M22, and M55, extending from just above the hydrogen burning limit to
the tip of the red giant branch, down to the white dwarf cooling sequence. We
have used the color-magnitude arrays to extract main sequence luminosity
functions (LFs) from the turnoff to about 0.13 solar masses. The LFs of M10 is
significantly steeper than that for the other two clusters. The difference
cannot be due to a difference in metallicity. A comparison with the LFs from
Piotto, Cool, and King (1997), shows a large spread in the LF slopes. This
spread is also present in the local mass functions (MFs) obtained from the
observed LFs using different theoretical mass--luminosity relations. The
dispersion in the MF slopes remains also after removing the mass segregation
effects by using multimass King-Michie models. The globular cluster MF slopes
are also flatter than the MF slope of the field stars and of the Galactic
clusters in the same mass interval. We interpret the MF slope dispersion and
the MF flatness as an evidence of dynamical evolution which makes the present
day globular cluster stellar MFs different from the intial MFs. The slopes of
the present day MFs exclude that the low mass star can be dynamically relevant
for the Galactic globular clusters.
