HEARTWOOD OF CRYTOMERIA JAPONICA 



847 



unilaterally or sporadically in a normal tree. This would be difficult to 

 explain on the variety hypothesis. The external differences often at- 

 tributed to the mature "black tree" (branches more pendulous than 

 normal, rind not so shaggy as that of "red tree," etc.) might be ex- 

 plained as the result of abnormal internal physiological conditions, a 

 high water content, for instance. The marked color change of "Sugi," 

 which occurs in winter on the needles of unshaded trees, might seem 

 to have an important bearing on the problem. The red coloring mat- 

 ters then produced we have found to be not anthocyanins but carotin 

 and xanthophyll. The constancy of leaf color is sometimes given as 

 one of the characteristics of "black tree;" this is not plausible as will 

 be seen when the evidence given later in this article has been consid- 

 ered. Although this is obviously another question and one in which 

 many factors are involved, it seems partly dependent upon the above 

 mentioned difference in water content. 



TRUE CAUSES OF THE DARKENING OE HEARTWOOD OE "SUGl" 



It seemed possible that the reason for our ignorance as to the cause 

 of the darkening of the heartwood of "Sugi" lay in the lack of any 

 detailed experimental observations. From a number of specimens 

 from both freshly felled and old air-seasoned wood we determined 

 the fact that hyphae are absent from the wood under discussion. The 

 discoloration was therefore assumed to be of a purely chemical nature 

 and the experiments showed : 



(a) Darkening of the fresh wood on exposure to air was entirely 

 removed by oxalic acid and the original color was instantly recov- 

 ered. But the normal "red wood" and some other coniferous woods 

 previously stained with catechol have been similarly faded on the 

 application of the same acid. 



(b) Chemical analyses of the heartwood of "sugi" showed the fol- 

 lowing results : 



Table 1. 



