8 



trees. As an illustration of the effect of the sun in some in- 

 stances we will cite the following. In 1893 a thrifty maple 

 standing in a small group of trees and exposed to the sun, was 

 tapped on the north and south sides. The excess in favor of 

 the south side was almost wholly due to the yield upon a day 

 when the sun shone brightly, but with the temperature but 

 slightly above freezing ; the yield was, south side, 1 1 [pounds, 

 north side, 2^ pounds. 



There can be little doubt as to the correctness of the com- 

 mon practice of tapping the south side whenever practicable. 



There is a growing tendency to tap trees twice, putting the 

 holes near together and letting the sap from both spouts drop 

 into the same bucket. To test the profit of so doing the following 

 trial was made : Six maples from twelve to sixteen inches in 

 diameter, standing near together and with the same exposure, 

 were divided into two groups, as nearly alike as possible in size, 

 spread of branches, etc. 



The trees in group A were tapped once with a y^ inch bit 

 and i^ inches deep. Those in group B were tapped twice, 

 once with a 5^ inch bit, and once with a ^ inch bit, the holes 

 being i^ inch deep and about 4 inches apart. Table 5 shows 

 the yield by trees and by groups. 



TABLE 5.— EFFECT OF TAPPING TREES ONCE AND TWICE. 



1892. 



March 25. 



" 26. 



28. 



30. 



1. 



4. 



10. 



12. 



16. 



April 



Group A. 

 Tapped once. 



14 



15 



16 



Group B. 

 Tapped twice. 



17 



18 



19 



17.7 lbs 



6.0 



7.5 

 19.0 

 20.0 



5-5 

 14.0 

 14.0 

 12.0 



18.5 lbs. 



7.0 " 



9.0 " 



22.0 " 



19.0 " 



4.0 " 



9.5 " 



13.0 " 



6.0 " 



12.7 lbs. 



6.0 " 



8.0 " 



21.7 " 



19.0 " 



8.0 " 



12.5 " 



15.0 " 



16.0 " 



19.0 lbs. 



8.2 " 



8.5 " 



22.0 " 



22.0 " 



5.0 " 



16.5 " 



23.0 " 



14.0 " 



Totalyield by trees..] 115.7 lbs. 108.0 lbs. 118.9 lbs. 138.2 lbs. 

 Total yield by groups 



342.6lbs. 



16.0 lbs. 

 6.0 " 



16.5 lbs. 

 4.0 " 



105.5 lbs. 1 87.5 lbs. 



331.6 lbs. 



The trees tapped but once gave slightly more sap than those 

 tapped twice. When we consider the similarity of the trees in 



