** :session evaluation on export
   :PROPERTIES:
   :DATE:     2010-09-01
   :END:
This first block is evaluated but /doesn't/ appear in export.

/:session *R* :exports none/
#+begin_src R :session *R* :exports none
  x <- 8
#+end_src

This second block /does/ appear in export.

#+begin_src R :session *R* :exports results
  x
#+end_src