I agree with Burkhard Leuschner that the term "morpheme" is being used to mean "lexeme," a unit with word-level meaning but which may be spelled 'with spaces' (like two or more words). The term lexeme also refers to single meanings; thus "bank" (the vault) and "bank" (the river wall) are two lexemes. "BE supposed to" would be one lexeme. I think that the problem here is that tradiitonal grammar does not have the sophistication to handle "BE supposed to" (as well as many other constructions). The value of traditional grammar lies in its simplicity, but that is its weakness, too. --Bill Murdick