  Different mechanisms believed to be responsible for the generation of bursts
in hydrodynamical systems are reviewed and a new mechanism capable of
generating regular or irregular bursts of large dynamic range near threshold is
described. The new mechanism is present in the interaction between oscillatory
modes of odd and even parity in systems of large but finite aspect ratio, and
provides an explanation for the bursting behavior observed in binary fluid
convection. Additional applications of the new mechanism are proposed.
