The flux of X-ray emission from F, G, and K giants drops abruptly at G5 III. This mimics the drop in rotation rates of giant seen previously. The X-ray flux, when normalized to the bolometric flux, varies as the square of the equatorial surface rotatin velocity. Lines formed in the chromospheric and transition region do not show such a close relationship with rotation, but are still correlated with it. Other H-R-diagram boundaries, such as the one for the V/R ratio for the Ca II K-line emission, appear not to be directly coupled to the stellar rotation.