HEARTWOOD OF CRYTOMERIA JAPONICA 865 



"particular substance" is transferred to the twigs by the above opera- 

 tion. As already shown in the course of this article, it means nothing 

 else than that the previous seasoning of the trunk prevents the lumber 

 from darkening, owing to the loss of moisture necessary to cause the 

 evolution of ammonia. In this connection the "girdling" method, 

 usually applied to teak trees in Java, will also be advisable for the 

 prevention of the extreme darkening of "Sugi." 



The lumber of "black tree" can be fairly well rid of the darkening 

 on exposure to air if it is submitted to somewhat rapid drying. The 

 stain of the lumber can be removed by treatment with any acid, organic 

 or inorganic ; for that purpose vinegar is ordinarily used in Japan. 

 A previous application of acid will also effectively prevent the 

 darkening. 



Though many other complicated matters associated with the indi- 

 rect cause of the darkening remain for further careful investigations, 

 it is evident at least that wounds can induce "black tree." Therefore, 

 the supposition that propagation by seedlings or slips of "red trees" 

 is the sole and safe means of the exclusive reproduction of "red tree," 

 and that "black trees" are a mere variety of "Sugi," is erroneous. 

 The additional precautions given above may be consulted with advan- 

 tage in this case. 



SUMMARY 



1. The heartwood of "Sugi" contains some "particular substance" 

 which shows a marked reaction with alkali and is responsible for the 

 darkening. 



2. All the heartwood of "Sugi" shows the darkening on the appli- 

 cation of alkali. 



3. The natural darkening of the heartwood is induced by wounds 

 and directly caused by ammonia evolved as the final decomposition 

 product of some organic substances. 



4. The conditions necessary to the darkening are air and moisture. 



5. Rapid seasoning can prevent the extreme darkening of the 

 lumber. 



6. The application of acid removes or prevents the darkening. 



7. The acidity of sap controls the phenomenon on the other hand. 



8. The whole discussion in this article is represented by the diagram 

 on page 866. 



