\item{file}{a file name specified by either a variable of mode character,
or a double-quoted string; if \code{file = ""} (the default) then the
tree is written on the standard output connection (i.e. the console).}
\item{file}{a file name specified by either a variable of mode character,
or a double-quoted string; if \code{file = ""} (the default) then the
tree is written on the standard output connection (i.e. the console).}