LETTER OF TRANSMITTAL. 
U. S. DeparTMENT or AGRICULTURE, 
Forest SERVIC#, 
March Age f Git: 
Sir: I have the honor to transmit herewith a manuscript entitled 
“Light in Relation to Tree Growth,” the major portion of which is 
the work of Mr. Raphael Zon, Chief of Silvics, and to recommend 
its publication as Bulletin 92 of the Forest Service. 
Respectfully, 
Henry S. Graves, Forester. 
Hon. James WIson, 
Secretary of Agriculture. 
