  We present a comparison of CN bandstrength variations in the high-metallicity
globular clusters NGC 6356 and NGC 6528 with those measured in the old open
clusters NGC 188, NCG 2158 and NGC 7789. Star-to-star abundance variations, of
which CN differences are a readily observable sign, are commonplace in
moderate-metallicity halo globular clusters but are unseen in the field or in
open clusters. We find that the open clusters have narrow, unimodal
distributions of CN bandstrength, as expected from the literature, while the
globular clusters have broad, bimodal distributions of CN bandstrength, similar
to moderate-metallicity halo globular clusters. This result has interesting
implications for the various mechanisms proposed to explain the origin of
globular cluster abundance inhomogeneities, and suggests that the local
environment at the epoch of cluster formation plays a vital role in regulating
intracluster enrichment processes.
