  Using a parameterisation of general self-adjoint boundary conditions in terms
of Lagrange planes we propose a scheme for factorising the matrix Schroedinger
operator and hence construct a Darboux transformation an interesting feature of
which is that the matrix potential and boundary conditions are altered under
the transformation.
  We present a solution of the inverse problem in the case of general boundary
conditions using a Marchenko equation and discusss the specialisation to the
case of graph with trivial compact part, ie. diagonal matrix potential.
