  For a graph embedded into a surface, we relate many combinatorial parameters
of the cycle matroid of the graph and the bond matroid of the dual graph with
the topological parameters of the embedding. This will give an expression of
the polynomial, defined by M.Las Vergnas in a combinatorial way using matroids
as a specialization of the Krushkal polynomial, defined using the symplectic
structure in the first homology group of the surface.
