  The (Michelson) Sivashinsky equation of premixed flames is studied in a
rectangular domain in two dimensions. A huge number of 2D stationary solutions
are trivially obtained by addition of two 1D solutions. With Neumann boundary
conditions, it is shown numerically that adding two stable 1D solutions leads
to a 2D stable solution. This type of solution is shown to play an important
role in the dynamics of the equation with additive noise.
