  Galactic Globular Clusters (GCs) containing bright X sources (L_x > 10^{36}
erg/s), commonly associated with Low Mass X-Ray Binaries (LMXBs), are found to
be significantly denser and more metal-rich than normal non-X-ray clusters both
in the Galaxy and in M31. Within a framework where LMXBs in GCs are generated
via tidal captures in high-density clusters and (2+1) encounters in low-density
globulars, the higher incidence of LMXBs with increasing metallicity is shown
to be {\it intrinsic} and not just a by-product of other effects. Two possible
mechanisms are examined: the first one assumes a dependence of the cluster IMF
on metallicity as recently published in the literature. The observed LMBXs,
more frequently occurring in metal rich clusters, agrees with the predicted
number of NS only if metallicity accounts for a minor contribution to the
observed variation of the IMF slope. Other alternatives explored, such as the
total variation of the observed IMF slopes is due to (a) just metallicity and
(b) the combination of metallicity and position in the Galaxy lead to a
clear-cut disagreement with the data. The second mechanism assumes that, at
fixed cluster density, the rate of tidal captures depends on radius and mass of
the capturing star. Based on standard stellar models, stars with higher metal
content have wider radii and higher masses, hence the rate of tidal captures
increases with increasing metallicity. From the order of magnitude computations
made, this new effect by itself could explain the observed ratio of 4 between
the frequencies of X-ray clusters in the metal-rich and metal-poor groups we
observationally determined. However, there is no reason to exclude that both
mechanisms can be at work.
