1912. 



PUBLIC DOCUMENT — No. 31. 



145 



variations in temperature, and that there would also be dili'er- 

 ences in the flow of sap and the translocation of plastic sub- 

 stances. That this is true is shown bv the fact that trees make 

 more growth on one side than on another, the more or less local- 

 ized photosynthesis causing a greater transmission of plastic 

 substances on that side. 



Some of these experiments were begun in 1907, a part of the 

 observations being made by Mr. IsT. F. Monahan, our former 

 assistant, while others were obtained in 1900 and later by Mr. 

 G. II. Chapman. 



These resistances were determined by a Weston Electric Com- 

 pany combination bridge, rheostat and galvanometer, provided 

 with a battery of 6 or 8 large Samson cells. 



Table I. — Showing Daily Records of Electrical Resistance (in Ohms) of 

 Maple {Acer saccharum, Marsh), April 7-26, 1907. Resistances taken 

 on the North, South, East and West Sides of the Tree at Midday. 



[Electrodes 10 feet apart. Mean daily temperatures given in degrees F.l 



