3(30 JOURNAL OF FORESTRY 



monia. Although it seems that "red wood" may also be able to evolve 

 ammonia, though perhaps in slight amounts, we must not leave out of 

 account the acidity of the sap, which is to be encountered by the 

 ?mmonia and which controls in large measure the darkening of the 

 wood. For example, No. 10, Table 3, owing to the marked acidity of 

 its sap (verified with litmus paper) ranged to the group of "red wood," 

 notwithstanding the fact that the same wood was very like "black 

 wood" as well in its appearance as in the content of "particular 

 substance." 



In connection with ammonia, some amino acids as the intermediate 

 decomposition product should be found in the wood. Yet, our experi- 

 ment fell short in verifying their existence beyond the fact that the 

 aqueous extract of the wood showed the tylosin reaction with Millon's 

 reagent. So its complete proof, together with that of the enzym decom- 

 posing the acids (desamidase), remains for further investigation. 



But it is evident that the conditions necessary for the production of 

 ammonia are the existence of both air and humidity as already shown 

 by experiment. Now considering the standing trees, the excess of 

 air can be supplied to the wood only by means of wounds, which at the 

 same time induce the transformation of sapwood into heartwood. 

 So "black wood" passes through the stage of being normal heartwood 

 and also is produced by a change in the sapwood. Of course, the 

 influence of the wounds upon these chemical changes in the trees may 

 vary with their sizes and other circumstances. Therefore, the heart- 

 wood of some trees can more or less go through the process of color 

 conversion, through the extreme influence of wounds, while still stand- 

 ing, whereas in others the conversion may be limited to the wounded 

 parts, depending on the healing of the wounds or the interruption of 

 the excess supply of air by other causes. But the heartwood of the 

 latter, where the decomposition of proteids was intercepted in the 

 middle of the process, can stain on exposure to air as has been 

 described. 



INDIRECT CAUSE OE THE DARKENING 



As was demonstrated in the previous paragraph, the wounds must 

 be the indirect cause of this phenomenon as suggested by Dr. H. 

 Shirasawa. To confirm this explanation, we carried out many inves- 

 ligations, including young and old trees, in the stands of the districts 

 of Yoshino and Shizuoka. In the young stands where the normal 



