Graphics from a remote host

Hi,
I'm using ssh to make use of R on a remote unix server.  Currently I  
save graphic output as pdf or ps files.  However, I'd like to be able  
to view some preliminary results in a graphic device before running  
big jobs.  Is it possible, e.g with port mapping, to tunnel graphic  
output from plot() back to my Mac desktop so I can view it directly  
with Apple's X11?

Thanks,

Matthew