14 College of Forestry 



111 opposition to I\. Hartig's conception, Frank (1884) 

 stated that these brown masses of woiind-giim in the dark- 

 ened areas — likewise the tyloses — are products of living 

 wood parenchyma. He reasoned that their formation is due 

 to a universal life process to afford protection by excluding 

 outside air from the li\'iiig wood so that^ the natural functions 

 of the latter are thereby kept undisturbed. lie therefore 

 called the wood thus darkened " protection wood." Frank 

 stated further that its formation can be induced artificially 

 by wounding and that one can cause it to be produced at 

 any desired position in a living tree. According to Frank 

 the protection wood is anatomically and physiologically iden- 

 tical to the heartwood which is to be found in most dicotyle^ 

 donous trees after a certain age. The benefit which the tree 

 receives through the closing of its woody elements to the 

 outer air by the '' protection wood " lies, according to Frank, 

 mainly in the fact that the air within the wood becomes inde- 

 pendent of atmospheric pressure. 



Temme (1885), working under Frank's direction, found 

 an increase in the specific gravity of the " protection wood " 

 over that of the sapwood. He stated that the penetration of 

 air and rain water through open vessels hastens the disinto- 

 gTation of the wood and also inaiiitained that the wood 

 browned by the infiltration of decomposition products offers 

 a certain protection against destniction. From his experience 

 in the care of trees, Temme concluded that the customary 

 covering of the smaller wounds with tar or tree wax was super- 

 fluous, since they are closed temporarily by the protective 

 wood until they are healed over, after which they are closed 

 permanently. 



It must be emphasized, however, that considerable credit 

 is due to Bohm (18Y9) who had disclosed all of the essential 

 features of protection wood several years before. He ob- 

 served (p. 221) that the pathological transformation to heart- 

 wood occurs predominatingly at the boundary between living 



