g54 JOURNAL OF FORESTRY 



We have next to take one more consideration into account. Mr. K. 

 Toyohira ^* suggested, in connection with his investigation of the 

 identification of "black tree," that an oxidizing enzym might be re- 

 sponsible for the phenomenon. Weevers '' found that the blackening 

 of the non-living parts of the plant is induced by the same enzym 

 oxidizing catechol. We examined the wood and found that the dis- 

 tribution of oxidizing enzym is confined to the fresh sapwood of both 

 red and black woods. So an oxidizing enzym does not come into play 

 in this case. 



In endeavoring to obtain a more reliable basis for the elucidation of 

 this phenomenon, we may well pay attention to construction work 

 using cement, concrete, mortar, etc. In these cases when strong 

 alkali comes into contact with the heartwood of "Sugi," a very ad- 

 vanced stage of the conversion can be seen at once. Experiments with 

 very dilute alkali induced fresh "red wood" to give the appearance of 

 natural "black wood." The fumes of ammonia were used to advan- 

 tage in this case, changing the tint immediately ; first to dark brown 

 and then to grayish brown, i. e., all stages which occur naturally in 

 "black wood" were exhibited within a short space of time. Parallel 

 tests with other kinds of wood have never given an equal darkening. 

 The above experiments favor the view that the "particular substance" 

 under question is one of the direct causes of this phenomenon, since 

 the sole part affected is the heartwood of "Sugi" and since this 

 "particular substance," giving a distinct reaction with alkali, is limited, 

 in its distribution among Japanese woods, to this same heartwood. 



Many tests and observations based on quite a number of pieces of 

 the wood of "Sugi" suggested the existence of a correlation between 

 the tint of the wood and the quantity of this substance, as well as 

 some chemical change of this substance at the time of conversion. 

 A set of colorimetric tests upon the aqueous extracts of many shavings 

 were therefore carried out to test the former assumption, utilizing 

 the marked color reaction with alkali. This showed that "particular 

 substance" is generally more abundant in the wood of denser tint, 

 agreeing with the well-known fact that "black wood" is usually more 

 or less dense colored. In regard to the second, assumption, we made 

 the following four sets of colorimetric tests in the same way. 



^^ Toyohira, Kinsuke. Identification of Red and Black trees of "Sugi" in 

 Kagoshin-.a-Province. Report of Alumni Association of Kagoshima High School 

 eif Agriculture and Forestry, No. 1, 1913. (In Japanese.) 



"Czapek, F. Biochemie der Pflanzen, Bd. II, Jena, 1905, p. 642. 



