Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class tetrapyrroles
                 Class chlorophylls
                   Class pheophytins
                     bacteriopheophytin a
                     bacteriopheophytin b
                     pheophytin a