  A novel phenomenological approach to the analysis of the conductivities of
incoherent layered crystals is presented. It is based on the fundamental
relationship between the resistive anisotropy $\sigma_{ab}/\sigma_c$ and the
ratio of the phase coherence lengths in the respective directions. We explore
the model-independent consequences of a general assumption that the
out-of-plane phase coherence length of single electrons is a short fixed
distance of the order of interlayer spacing. Several topics are discussed:
application of the scaling theory, magnetoresistivity, the effects of
substitutions and the intermediate regime of conduction when both coherence
lengths change with temperature, but at different rate.
