[R] What fontfamily x11() device normally uses?

[M.Kondrin]

Hello!
Can I somehow set x11 device to use font different from default 
helvetica-arial (times for example?)? Is this font hardcoded into R or 
can I substitute some other system font? Does x11 device use 
standard/user-supplied .Xresources file (under Linux)?
The questions are the same for gtk() device (with .gtkrc substituted for 
.Xresources).
Thanks in advance.