  We present results from a near-infrared $K$-band imaging survey of 59
elliptical galaxies in five nearby clusters. We measure photometric parameters
for each galaxy using surface photometry and draw velocity dispersions from the
literature. Three observables define a near-infrared Fundamental Plane (FP) of
elliptical galaxies with $R_e \propto \sigma^{1.44\pm0.04}
\Sigma_e^{-0.79\pm0.04}$. The scatter in the near-infrared relation is small at
$16.5$\% in distance, which is equivalent to, or less than, the scatter of the
optical FP. We suggest that the small deviation of the near-infrared FP
relation from the optical FP is due to the reduction of metallicity effects in
the near-infrared bandpass. While the small scatter of the optical FP could be
consistent with compensating effects of age and metallicity, the similarly
small scatter of the near-infrared FP is nearly independent of metallicity and
hence places a strong constraint on possible age spreads among elliptical
galaxies at every point along the FP. We suggest that the departure of the
near-infrared FP from the pure virial form $R_e \propto \sigma^2
\Sigma_e^{-1}$, and the corresponding observed relation $\left( M/L \right)
\propto M^{0.16\pm 0.01}$, may be explained by slight systematic departures of
the structure and dynamics of elliptical galaxies from a homology.
