Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       particles
         hadrons - composite particles
           mesons - bosonic hadrons
             1 light unflavored mesons
             2 strange mesons
             3 charmed mesons
             4 charmed, strange mesons
             5 bottom mesons
             6 bottom, strange mesons
             7 bottom, charmed mesons
             8 c cbar mesons
             9 b bbar mesons