  Lando framed graph bialgebra is generated by framed graphs modulo 4-term
relations. We provide an explicit set of generators of its primitive subspace
and a description of the set of relations between the generators. We also
define an operation of leaf addition that endows the primitive subspace of
Lando algebra with a structure of a module over the ring of polynomials in one
variable and construct a 4-invariant that satisfies a simple identity with
respect to the vertex-multiplication.
