surveys in §3.6.

In the next section we provide a brief summary of the observations and data reduction. In §3 we compile the catalog of candidate cluster members with measured rotation periods. In §4 we fit analytic models to the observed period-color sequence in M37. In §5 we compare the photometric observations to spectroscopic $v \sin i$ measurements for a number of these stars. In §6 we study the amplitude distribution as a function of period and color. In §7 we study the Blue K dwarf phenomenon in M37. In §8 we compare these observations to theories of stellar angular momentum evolution. We discuss the results in §9.

Summary of Observations
=======================

The observations and data reduction procedure were described in detail in Papers I and II, we provide a brief overview here. The observations consist of both $gri$ photometry for $\sim 16000$ stars, and $r$ time-series photometry for $\sim 23000$ stars obtained with the Megacam mosaic imager [@McLeod.00] on the 6.5 m MMT. We also obtained high-resolution spectroscopy of 127 stars using the Hectochelle multi-fiber, high-dispersion spectrograph [@Szentgyorgyi.98] on the MMT.

The primary time-series photometric observations were done using the $r$ filter and consist of $\sim 4000$ high quality 