Note by the Editor 



The investigation described in this bulletin was under- 

 taken by the Botanical Department of the Pennsylvania 

 State College in co-operation with the Department of In- 

 dustrial Research of the University of Pittsburgh, now 

 known as the Mellon Institute of the University of Pitts- 

 burgh. The investigation was begun in March, 1912, and 

 continued about one year and a half. 



The Mellon Institute desires to express its apprecia- 

 tion of the co-operation of State College and to thank Mr. 

 J. F. Clevenger, who carried on the investigation. 



JOHN O'CONNOR, JR. 



