6 



WESTEKN PINES AS A SOUKCE OF NAVAL STORES. 



stand on one of the experimental areas. The number of cups per 

 acre varied from 37 in area A to 87 in area C. The trees were divided 

 into two classes, " yellow pine" and " black jack/' and the dip from 

 each class collected separately. The name ' ' black j ack ' ; is commonly 

 used for young western yellow pine with black, deeply furrowed bark 

 and a comparatively dense crown. Later in life the bark becomes 

 orange and smoother, and the tree is then called " yellow pine." 

 The period in the tree's life at which the change takes place is varia- 



FIG. 1. Location of experimental areas in Arizona. 



ble, and it is fairly common to find black jack of considerably larger 

 diameter than yellow pine growing close by. Table 1 shows the 

 number and size of the tapped trees in each of the three areas, A, 

 B, and C. 



The average size of the trees in area A was greater than that in 

 B or C. In area C the stand was denser and the trees more uniform 

 in size than in the other two areas. Yellow pine predominated in 

 areas A and B, while in C the stand was composed mainly of black 

 jack. 



