An. Rpt. Office of Experiment Stations, 1906. 



Plate XIV. 



r 

 > 



2 

 CO 



-n 

 O 



33 



o 



o 

 z 

 o 



33 



> 



c 

 -f 

 o 



o 



O) 



r 

 c 



o 

 m 



O 

 > 



H 

 m 



