  We report a detailed optical study of the clusters Abell 2125 and 2645. Both
clusters have z=0.25 and richness class 4, yet contrast strongly in blue
fraction and radio galaxy population. We find 27 spectroscopically confirmed
radio galaxies in the blue cluster, A2125 and only four in A2645. The excess
radio population in A2125 occurs entirely at L(20cm) < 10^23 W/Hz, where one
expects star-formation to be responsible for the radio emission. Most of the
radio galaxies have optical properties consistent with types later than E/S0,
but emission lines weaker than would be expected for the SFR's implied by the
radio emission. Thus we suspect dust obscuration is important. The cluster-
cluster merger in A2125 seems likely to play a part in these phenomena.
