Bui. 181, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate III. 



31 

 a 



> 



D 



m 

 cn 



> 



cn 

 O 



ro m 



< m 



o H 



c > 



X -n 



> 



H 

 m 



H 

 I 

 m 



cn 



rn 

 > 



