36 



RICHTHOFEN 



NATURAL SYSTEM 



=51 



I 



•3 ."S ^j 



f 3 5 o 



^ 3 s 





t 3 



6 A 



a 





O t* 



a 

 ■of 



En 



4 



o 





i 



&3 



Cj *^ O 



(74) 



