RESIN IN BLED AND UNBLED TREES. 343 



The explanation offered in the preceding paragraph gains still more probability when trees 60 

 and 61 are compared with each other and also with 52 and §3. The difference between 1 and 2, the 

 results of average analyses — all these are very suggestive of the theory that the sap, and not the 

 heart of the tree, supplies the turpentine when the tree is tapped. The fact that the heartwood of 

 trees felled one year after tapping is fully as rich or as poor as that of trees felled five years after 

 tapping, seems to the writer of especial significance, for it shows that the richness of the heart- 

 wood in a tapped tree is independent of time of rest before felling. 



It is a well-known fact that when a pine tree is cut transversely, liquid turpentine immedi- 

 ately appears on the fresh surface of the sapwood, while the heartwood remains perfectly clear. 

 It would seem as if the turpentine in the sap is far less viscid than that in the heart of a tree. It 

 is probable that the turpentine in the sap is richer in volatile hydrocarbons than that in the heart. 

 (A difference of cell structure and manner of existence of oleoresins may also account for this 

 difference in part. — B. E. F.) 



It is generally stated that crude turpentine as obtained on a large scale yields from 10 to 25 



T 

 per cent of volatile oil. This gives -g-= 11.11 to 30, with an average of over 20. This average 



T 

 is somewhat higher than that for the p as found for the turpentine from heartwood of the 21 



trees analyzed. Although experimental data are wanting to show conclusively that the difference 

 in the consistency of the oleoresin from sapwood and heartwood is due to a difference in the 

 relative amount of volatile oil, yet it is quite probable that this should be the cause. The oleoresin 

 in the heartwood of trees has been produced for the most part when the 'heartwood was yet 

 sapwood. Therefore that j>art of turpentine which is found in the heartwood is the oldest in age 

 and consequently has been exposed the longest to oxidizing influences of air, which gradually 

 replace the water when the sapwood changes to heartwood. It is the same kind of oxidation and 

 of thickening which takes place when crude turpentine is exposed to the air and sun, or when a 



rp 



fresh cut is made in the bark of a tree. It is probably for the same reason that ^-becomes smaller 



as we approach the pith of the tree, because the parts nearest the pith are the oldest. 



It is difficult to conceive how the thick oleoresin of the heartwood could be made to flow 

 toward the incision when a tree is tapped. It is also difficult to explain by what means the tree 

 could change this thick turpentine into a less viscid solution in order that it may flow toward the 

 wound. 



One would judge, a priori, from the great difference in the consistency of the turpentine in the 

 heart and sap that only the liquid turpentine will flow when a tree is tapped. Tapping will then 

 have little effect, if any, upon the oleoresin stored up in the heartwood of the tree. A tree whose 

 heartwood is rich in turpentine will remain so after tapping. 



The writer is not willing to generalize too hastily from so few results and consider them as a 

 solution of the jjroblem. A large number of analyses, devoid of the possibility of chance selection 

 of samples, is necessary before a positive or a negative answer can be given to the question, does 

 the tapping of trees for turpentine affect the subsequent chemical composition of the heartwood? 



But, however few in number the results are, they admit of the following conclusions: 



(1) Trees that have been tapped can still contain very much turpentine in the heartwood. 



(2) Trees that have been abandoned for only one year before felling can contain fully as much 

 turpentine in the heartwood as trees that have been abandoned for five years. 



(3) Trees that have not been tapped at all do not necessarily contain more turpentine in the 

 heartwood than trees that have been tapped. 



The following diagram serves to show what proportion of each disk was involved in each of 

 the detail analyses, and the results in each case. The right-hand vertical line represents the pith 

 of the tree, the horizontal lines represent the radical extension of each disk, as numbered by roman 

 number, the position of the disk in the tree being maintained as in nature, IV being the top, II 

 the lower, and III the intervening disk. The subdivisions of radii represent the actual divisions 

 of the disk to scale of one-half natural size, the portions to the left of the heavy subdivision line 

 representing sapwood s 1 and $ 2; the portions to the right heartwood 7i, h, divided according to 

 the method as indicated above. The four columns of figures over each disk piece represent results 

 pertaining to that piece; they stand m order from the top for (1) number of rings, (2) volatile 



