858 JOURNAIv OF FORESTRY 



(II) On the application of concentrated alcoholic extract of heart- 

 wood, sapwood of "Sugi" and other coniferous woods shows a some- 

 what similar color to that of "black wood." Parallel tests with catechol 

 solution (prepared by treating catechol first with ferric chloride and 

 then with alkali) gave similar results. 



(III) The drops of dilute alkali put upon the heartwood become 

 red in color while the parts of the wood in contact with the drops 

 change to dark brown. 



(IV) The red change of the cell walls upon the application of alkali 

 can be seen only under the microscope. 



The difference between the color reaction of the infusion and that 

 of the wood is only an optical phenomenon differing with the media. 

 It therefore seems possible that the auxochrome of this darkening is 

 an hydroxyl group which reacts markedly to the chromogen peculiar 

 to "Sugi." The fact that it is somewhat difficult to extract heartwood 

 with water after darkening favors this conclusion agreeing with the 

 general fact that the hydroxyl group is not only effective in coloring 

 the chromogen but also fixes the coloring matter in animal and vege- 

 table fibers. 



Much valuable assistance for a satisfactory explanation can be 

 secured from the following experiments which demonstrate the pres- 

 ence of an hydroxyl group in the darkening process : 



(I) Litmus-paper inserted in the sawdust of the green "black wood" 

 or closely wrapped in a shaving showed an alkaline reaction when the 

 darkening began. 



(II) Some of the same papers were put between boards, including 

 some of sapwood, prepared from green "black wood." They showed 

 an alkaline reaction where darkening had taken place and correspond- 

 mg in its intensity to the intensity of the darkening. The reaction was 

 most intense on the outer parts of the heartwood where there was a 

 better circulation of air. 



(III) The alkaline reaction was not observed in the sapwood of 

 "black tree" or the heartwood of "red tree." 



In view of these facts, it becomes evident that all the heartwood of 

 "Sugi" can get the darkening with alkali, and that the darkening of 

 "black wood" is caused by the auxochrome naturally raised in the 

 heartwood on exposure to air while the wood is submitted to prolonged 

 gentle seasoning. 



