An explanation of the excited-state structure of the FMO (Fenna-Matthews-Olson) complex of Prosthecochloris aestuarii is given from the point of view that the dipole-dipole interactions among the bacteriochlorophylls of the unaggregated C-3 symmetric trimers observed in the cyrstalline state are mainly responsible for the key features of the "linear" absorption characteristics (absorption, linear dichroism, and singlet-triplet absorption difference) in the Q(y) region.