\item{i}{indices of the tree(s) to select from a list; this may be a
vector of integers, logicals, or names.}
\item{name}{a character string specifying the tree to be extracted.}
\item{i}{indices of the tree(s) to select from a list; this may be a
vector of integers, logicals, or names.}
\item{name}{a character string specifying the tree to be extracted.}