A fluorescence band at 628 nm seen in certain preparations of chlorophyll on polyethylene particles swollen with tetradecane comes not from an impurity of protochlorophyll in the original chlorophyll, but from a substance like protochlorophyll formed upon adsorption of chlorophyll to the particles. Much of the chlorophyll is grafted to polyethylene in the same particles by a process that does not affect the chromophore. These and other properties peculiar to the particles are tentatively ascribed to a prior free radical oxidation process in the swollen particles.