Building tree on Mac OS X Lion 10.7.4Edit
$ curl -O http://mama.indstate.edu/users/ice/tree/src/tree-1.6.0.tgz
$ tar xzf tree-1.6.0.tgz
$ cd tree-1.6.0
$ vim Makefile
$ make # comment out Linux section, uncomment Mac OS X section
$ sudo make install
$ curl -O http://mama.indstate.edu/users/ice/tree/src/tree-1.6.0.tgz
$ tar xzf tree-1.6.0.tgz
$ cd tree-1.6.0
$ vim Makefile
$ make # comment out Linux section, uncomment Mac OS X section
$ sudo make install