[ESS] R doesn't function in *R* buffer after "M-x R"

[pleydell at supagro.inra.fr]

>> But as Emacs initializes exec-path from the active PATH when emacs
>> starts,  the correct solution really is to make sure  R  is in your
>> PATH
>> independently of emacs, and then, also  M-x R  will work fine.
>
> Thanks for pointing that out; of course, the best solution is to set
> PATH outside of Emacs!
>
> Stephen

I don't get it. I forgot to mentioned in my original post that my .bashrc did
contain the lines

PATH=$PATH:/home/david/lib/emacs23/bin
export PATH
PATH=$PATH:/home/david/lib/R-2.10.0/bin
export PATH

but this was not enough to get M-x R working in emacs. I suppose emacs 
needs to
know where to find .bashrc or that I use bash and not some other shell, but I
do use the default location (~/.bashrc) so why was this not a solution?

regards
David