My object has been to gather together various combinatorial results on labelled trees. The basic definitions are given in the first chapter; enumerative results are presented in the next five chapters, classified according to the type of argument involved; some probabilistic problems on random trees are treated in the last chapter. Some familiarity with matrices and generating functions is presupposed, in places, but much of the exposition should be accessible to anyone who knows something about finite mathematics or probability theory.
This material was originally prepared for a series of lectures I gave at the Twelfth Biennial Seminar of the Canadian Mathematical Congress at the University of British Columbia in August, 1969. I am indebted to Professors Ronald Руке and John J. McNamee for their invitation and encouragement.