  We present new results from a systematic study of absorption line strengths
of galaxies in clusters approaching redshifts of unity. In this paper, we
specifically compare the strengths of the high-order Balmer absorption features
of Hgamma and Hdelta in E/S0s in the four clusters Abell 2256 (z=0.06),
CL1358+62 (z=0.33), MS2053--04 (z=0.58), and MS1054--03 (z=0.83). By comparing
the correlation of Balmer line strength with velocity dispersion for E/S0s in
the three clusters, we find moderate evolution in the zero-point of the
(Hdelta_A+Hgamma_A)-sigma relation with redshift. The trend is consistent with
passive evolution of old stellar populations. Under the assumption that the
samples can be compared directly, we use single-burst stellar population
synthesis models to constrain the last major occurrences of star-formation in
the observed E/S0s to be z_f > 2.5 (95% confidence). We have compared the
evolution of the Balmer absorption with the evolution of the B-band fundamental
plane and find that simple stellar population models agree very well with the
data. While the best agreement occurs with a low value for Omega_m, the data
provide strong confirmation of the time-evolution in recent stellar population
models.
