The barium and R type stars

( UBVRI ) photometry of Rand barium stars (including CH stars) is discussed in connection with the red giant branch of the old disk population (Wolf 630 Group and M67 cluster). Luminosity calibrations are obtained from membership in moving groups, clusters or wide binaries and from Olin Wilson's observations of H and K emission widths. Barium and R stars may only be present amongst objects of two or three solar masses or less. It is concluded that old disk population N stars represent the short, core-helium ignition stage of 1 to 2 solar mass stars which then either pass to the M variable stage before becoming asymptotic branch (barium) stars, or vice versa.