This paper takes up the
function theoretic approach to the study of ultraspherical expansions, their
conjugates, the associated elliptic equations, and first order systems. The theory of
pseudo analytic functions and Bergman-Gilbert type integral operators are employed,
and the relation between these two approaches is examined. Throughout, results
obtained are analogs of well known theorems from the theory of analytic functions of
a single complex variable, and the related study of harmonic functions and Fourier
series.