722 PROPERTIES, HARVESTING AND DISPOSAL OF RESIN. 



stem, however, becomes saturated with resin and does not decay. 

 There is a considerable loss of timber, owing to the grooving. 



The black pine yields from 2J to 4^ kilos (5J to 10 pounds) 

 of crude resin per tree annually ; 50 pounds of the crude resin 

 yield 7 to 10 pounds of oil of turpentine, and about 30 pounds 

 of colophany. 



SECTION V. YIELD OF KESIN AND EFFECTS ON THE TREES OF 

 EESIN-TAPPING. 



Practical experience in resin-tapping gives the following 

 annual yield of crude resin per tree, for the various species, 

 the reduction in resin is approximately proportional to the 

 coolness of the climate : 



Pinus Khasiana . . . 15 Ibs. 

 ,, Merkusii . . . 13 ,, 

 ,, palustris . . . 9*25 

 ,, Pinaster . . . 6 -6 ,, 

 ,, longifolia . . . 5*5 ,, 

 austriaca . . . 4'6 ,, 

 Do (old trees) . . 8'36 

 excelsa .... 2'64 ,, 

 Picea excelsa . . . . 1*1 

 The usage is leased on a definite area, or at so much a tree 

 annually. In the latter case the height of the groove is 

 limited. The resin may be harvested also by the forest 

 manager and the resin sold. 



The effect on the trees of resin-tapping, according to Mayr, 

 does not involve a deterioration of the heartwood, either in 

 specific weight, strength or durability. This has been proved 

 by experiments made by Gomberg* in the strength of tapped 

 and untapped trees. The sapwood is said to become less 

 durable, its durability is little enough in any case. Never- 

 theless the consequent deterioration in the utility of the 

 timber is considerable. That resinous wood is formed around 

 the grooves is not unimportant. Stoger and Seyffertt have 

 proved that cones and seeds of tapped pines are small and that 

 the seedlings are weak, though no degeneration of the trees 



* United States Department of Agriculture. " Forestry Bull." 8, 1893. 



t /entralblatt f. das gcs. Korstwesen." 1*7S, 1SS.V 



