Polarimetric observations of the red semi-regular variable L2 Puppis, obtained over a period of several years, confirm significant variations across the CaI 4226 line and several TiO bands. Together with published infra-red data, the observations point to a fundamental symmetry plane to which all variations with wavelength and time are related. The data are also consistent with a combination of photospheric effects, including a non-uniform distribution of calcium across the stellar disk, and scattering from grains in a cloud in which there is a systematic variation in grain size with distance to the star. Grain growth and dissipation, as evidenced by the observations, occur on a time scale of several years, in contrast to the optical variability time scale of months.