Changing font throught matplotlibrc file


I am trying to change the default font by adding the following lines
to the matplotlibrc file:

## FONT : serif
font.serif : Palatino

However, I get the following error.

UserWarning: findfont: Font family ['serif'] not found. Falling back
to Bitstream Vera Sans
  (prop.get_family(), self.defaultFamily[fontext]))

If I just use: : serif

I get a serif font (that is not Palatino). I certainly have Palatino
on my machine (Mac OS X 10.5.8).
Am I doing something wrong? If I want all text to be some font, is
there a way to change it in matplotlibrc file?

Thanks for your help.