Memory clear problem

Hello.

I think this is a simple problem.  I have R running a program which generates variables that it 'remembers'.  The trouble is that I've modified the file that it's generating these variables from but doesn't seem to realize that.  When I type 'trees' - I get the same data set produced.

I tried shutting R down and not saving the workspace, but when I open 'er up again and type 'trees', there is that same data set.  I saw a memory clear command somewhere in one of the help files but I'll be danged if I can locate it now.

Please tell me this is a simple problem with a nice(one-line) solution.

Thanks,
Suzanne