By following an idea of Nicodemi we study certain sequences of extensi
on operators for multilinear mappings on Banach spaces starting from a
ny given extension operator for linear mappings. In this way we obtain
several new properties of the extension operators previously studied
by Aron, Berner, Cole, Davie and Gamelin. As an application of our met
hods we show the existence of plenty of unbounded scalar-valued homomo
rphisms on the locally convex algebra of all continuous polynomials on
each infinite-dimensional Banach space. This improves a result of Dix
on.