  We extend the search for fermionic subspaces of the bosonic string
compactified on E8 X SO(16) lattices to include all fermionic D-branes. This
extension constraints the truncation procedure previously proposed and relates
the fermionic strings, supersymmetric or not, to the global structure of the
SO(16) group. The specific properties of all the fermionic D-branes are found
to be encoded in its universal covering, whose maximal toroid defines the
configuration space torus of their mother bosonic theory.
