  The paper deals with affine 2-dimensional Toda field theories related to
simple Lie algebras of the classical series ${\bf D}_r$. We demonstrate that
the complexification procedure followed by a restriction to a specified real
Hamiltonian form commutes with the external automorphisms of $\mathfrak{g}$.
This is illustrated on the examples ${\bf D}_{r+1}^{(1)} \to {\bf B}_r^{(1)}$
and ${\bf D}_4^{(1)} \to {\bf G}_2^{(1)}$ using external automorphisms of the
corresponding extended Dynkin diagrams.
