DISTRIBUTION OF EEHIN. 705 



In order to compare the contents in resin of foreign trees 

 with that of German trees, the percentage of resin in 

 absolutely dry wood is given below : 



Grammes. 



Norway spruce 0'896 



Bavarian silver-fir . . . . . 1'213 



spruce ..... 1'498 



N. American Douglas-fir . 1*934 



Tyrolese larch 2*340 



Norway pine ...... 2*426 



Alpine mountain-pine .... 3*040 



Hamburg Douglas-fir .... 3*892 



Bavarian plateau larch .... 4*588 



Danube valley pine ..... 5'240 



Bavarian Weymouth pine . . . 6*704 



N. American ,, . . . . 7*876 



,, Pitch-pine (Pimis paliistris) . 8*278 



The above table shows that Weymouth pine is richest in 

 resin of all German conifers, then in succession, common pine, 

 larch, spruce and silver-fir. Douglas-fir is intermediate 

 between spruce and larch, while pitch pine is more resinous 

 than all the other conifers. Absolutely dry branchwood and 

 rootwood also contain the following percentage of resin: 



Branchwood of spruce .... 5*909 



Kootwood .... 9'857 



Branchwood ,, larch .... 4*400 



Eootwood .... 5*835 



Every exposed wound in a tree causes an abnormal local 

 amount of resin, as the tension of_the internal tissues presses 

 the resin over the wound, and after the water in the sap has 

 evaporated, the resin flows into the cell-walls and cell- 

 lumina. This resinosis does not occur in wounds of the 

 heartwood, for there is no flow of resin from heartwood. 

 Fungi, such as Armillarea mellea, Fomes annosus (Trametes 

 radiciperda), Dasyscypha calycina (Peziza), Pestalozzia, Perider- 

 ni i urn, etc., also cause a flow of resin, and resinosis; at the 

 rootstock, especially of pines, by decay, the resin is driven 



P.U. Z Z 



