15.64.31.19  TREE   - Searches the entire directory tree for the histogram
starting with the current area.  This option  remains  set  from  one  SET
HISTOGRAM  command to the next.  You may only search a directory tree in a
forward directions so this does not work for the option PREVIOUS or  LAST.
Essentially  the  first time you specify TREE the entire directory tree is
setup for a search.  Subsequent SET HISTOGRAM commands should not use  the
TREE option unless a new search is desired.