HEARTWOOD OF CRYTOMERIA JAPONICA 863 



and its behavior in drying are possibly induced by the water adsorption 

 power of the wood, which may be supposed to be further caused by 

 its high content of accessory sulstances in the heartwood. The in- 

 crease in the amount of "particular substance" and other organic sub- 

 stances, from which ammonia is derived, serves as an explanation. 

 The extraordinary case found among even "red wood" (such as No. 8, 

 Table 8) also can be explained in the same way, as this material came 

 from the same source as No. 10, Table 3, which also showed an excep- 

 tionally high content of "particular substance" for "red wood." But, 

 as the origin of the rich production of such substances in "black wood" 

 and especially that of the marked acidity of the sap, are beyond reach 

 as yet, w^e presume here conveniently from the general occurrence of 

 the phenomenon, that the^e matters are indirectly derived from the 

 site. Although the future will probably reveal the exact and precise 

 factors, possibly associated with "black tree" as a variety^ it must be 

 related only to the rich production of these substances and the acidity 

 of the sap. 



"black tree" in reeation to site, age, etc. 



As "black wood" is indirectly caused by wounds, it follows that 

 very many "black trees" are naturally located on the places where 

 trees are apt to get wounds, such as the margins of woodlots, ravines, 

 road and trail sides, stands closely located to dwellings, places where 

 there are rolling stones caused l3y loosening the rocks, the sides of 

 slides or other roads, etc. Insects and artificial pruning may some- 

 times cause the effective wounds. 



Calcareous, fertile, and swampy lands are apt to produce "black 

 tree." These physiographical conditions, especially soil properties, 

 seem to be largely responsible for the rich production of "particular 

 substance" and other unknown organic substances, in short, "heart- 

 wood substances," and subsequently influence the extent and color 

 intensity of the darkening. In this connection, the acidity of sap, 

 which controls the darkening, is also possibly related to the same 

 factors. For example, the extraordinary acidity of sap is the only 

 explanation suggested for the occurrence of the "red tree" which had 

 three points of similarity with "black tree," i. e., wounds, large quanti- 

 ties of both "particular substance" and water (as already shown re- 

 spectively in No. 10, Table 3, and in No. 8, Table 8) and the similar 

 external appearances of the tree and the heartwood. Although the 



