Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             reactive intermediates
               Class radical ions
                 Class radical cations [X•+, X:+]
                   Class nitrenium ions [R2N:+]
                     Class iminylium ions [R2C=N:+]