[R] A question about boxplot: mean and median

[R_xprt_wannabe]

Dear List,

I have worked through the examples given in the help
on boxplot().  If I am reading it right, only the
median is produced (as a default), which is
represented by the horizontal line inside the box. 
What argument do I need to specify if I want to show
the mean as well?

Thanks,

platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    0.0            
year     2004           
month    10             
day      04             
language R