Dependence of red-sequence GLFs on cluster X-ray luminosity in the B,V,R, and I rest-frame bands (from left to right) for clusters stacked together. The top line is for clusters with X-ray luminosities 8 × 10⁴³<L_X< 10⁴⁵ erg s^-1 and the bottom line is for clusters with X-ray luminosities L_X> 10⁴⁵ erg s^-1. Red crosses are red-sequence GLFs normalized to 1 deg². The vertical red lines indicate the 90% completeness limit. Red curves are the best Schechter fits to red-sequence galaxies. The slope of the fit α is given with the number of clusters and the mean redshift of the stack.