  We study linear series on a general curve of genus g, whose images are
exceptional with respect to their secant planes. Each such exceptional secant
plane is algebraically encoded by an included linear series, whose number of
base points computes the incidence degree of the corresponding secant plane.
With enumerative applications in mind, we construct a moduli scheme of
inclusions of limit linear series with base points over families of nodal
curves of compact type, which we then use to compute combinatorial formulas for
the number of secant-exceptional linear series when the spaces of linear series
and of inclusions are finite.
