Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class alkaloids
                 Class pyrrolizidine alkaloids
                   acetylsenkirkine
                   desacetyldoronine
                   doronine
                   florosenine
                   integerrimine
                   mucronatinine
                   otosenine
                   retronecine
                   retrosine
                   senecionine
                   senecivernine
                   senkirkine
                   usaramine