We show that an equivariantly embedded Hermitian symmetric space in
a projective space which contains neither a projective space nor a
hyperquadric as a component is characterized by its fundamental forms
as a local submanifold of the projective space. Using some
invariant-theoretic properties of the fundamental forms and Seashi's
work on linear differential equations of finite type, we reduce the
proof to the vanishing of certain Spencer cohomology groups. The
vanishing is checked by Kostant's harmonic theory for Lie algebra
cohomology.