IIKARTWOOD OF CRVTOMERIA JAPONICA 845 



who are endeavoring to control the phenomenon as well as to throw 

 some light upon the general question of the natural staining of woods. 



PREVIOUS HYPOTHESES AS TO THE CAUSE OF BLACK HEARTWOOD OF 



''SUCi" 



The heartwood of "Sugi" (Cryptomcria japonica Don.) is normally 

 reddish. This ordinary heartwood of trees called "red tree" is some- 

 times replaced by dull red or reddish brown wood known as "black 

 wood," "black Sugi," or "black heart." These unusual colors turn to 

 dark brown on exposure to air, bleaching out gradually to grayish 

 brown. It is not uncommon for all the trees of one "compartment" 

 to produce this kind of wood almost exclusively. Mention must be 

 made of the case where the color change above described takes place 

 while the tree is still standing, the reason for this will be discussed 

 later in this article. 



The wood put on the market varies in tint from pink, reddish, red, 

 dull red, to reddish brown or even grayish brown. It is usually uni- 

 formly colored, but sometimes longitudinal bands of more or less 

 normal colored heartwood alternate with dull or deep colored streaks. 

 Brownish or dark colored wood is usually of lower price, especially 

 when it is used as cooperage material. Staves from this dark lumber, 

 for instance, are sometimes valued at only one-fifth of the price of 

 that of high quality. The phenomenon has accordingly attracted the 

 universal attention of thoughtful foresters • in all districts, actuated 

 not only by the economic point of view but also interested in the fact 

 that the phenomenon is peculiar to "Sugi." 



Up to the present, however, the cause of the phenomenon has re- 

 mained quite unknown, although three hypotheses have been put for- 

 ward to explain it. (1) That it is due directly to some ferrous com- 

 pounds locally abundant in the soil. (2) That it is due indirectly to the 

 site. (3) That these "black \vood" trees belong to a separate variety. 



] . The direct chemical hypothesis is diametrically opposed to the 

 truth as will be shown later. Moreover, this hypothesis is rendered 

 impossible by the occurence side by side in the same stand of normal 

 "red trees" and "black trees," and particularly by those cases of uni- 

 lateral distribution in the same trunk. It also does not explain why the 

 darkening is confined to the heartwood of "Sugi" while Castanea and 

 Pasania. both of which are rich in tannin can grow side by side with 

 "black trees" without any trace of darkening in their woods. There 

 are very few references to this kind of wood-staining which have 



