Using picosecond fluorescence spectroscopy, we demonstrated antenna size dependent exciton dynamics in chlorosomal antenna, measured for intact cells of different cultures of the green bacterium Chloroflexus aurantiacus with different chlorosomal antenna size determined by electron microscopic examination of ultrathin sections of the cells. The measured bacteriochlorophyll (BChl) c excitation lifetimes show a quasilinear dependence on chlorosome size as predicted in our model for cylindrical exciton migration within the three-dimensional chlorosomal antenna. The migration model was developed for the proposed exciton model of chlorosomal BChl c aggregation. The data predict the time constant values for excitation energy transfer between BChl c aggregates as well as to BChl a of the baseplate.