4<S WRIGHT : THE GENUS DIOSPYROS 



uncertainty has long been recognized by persons engaged in 

 financial speculations, and too much stress cannot be laid on 

 the individual variation which occurs in trees of the same 

 species from the same or different localities. 



On the other hand, there can be no question as to the 

 specific tendencies to produce a definite type of heartwood, 

 though even here one has to -allow a wide range of vari- 

 ability for each species. For instance, the heartwood of JD. 

 Melanoxylqn and D. Ebenum is almost invariably jet black, 

 and on this account these two species provide the greater 

 part of ebony from India and Ceylon ; D. insignis, on the 

 other hand, never yields a black heartw6od, D. Gardner! 

 always produces a yellow wood, and J). Moonii a timber 

 which is of a red tint spotted here and there with small black 

 strands. There could be no possible doubt of the species 

 were the timbers of ~Q. Ebenum, D. Kurzii, D. insignis, 

 and J). quaesita to be mixed with one another, as their 

 macroscopic characters are so pronounced. 



The specific colour tendencies are somewhat difficult to 

 explain. The two factors which determine the colour of the 

 timber in the respective species are : (1) the means of distribu- 

 tion of the coloured substances ; (2) the proportion of coloured 

 gum and resin present in the tissues. 



It is perhaps safe to assume that the best or most general 

 distribution of coloured substances will be effected in those 

 xylems the elements of which are freely communicating 

 with one another, and therefore those species the timbers of 

 which contain a high percentage of medullary ray cells and 

 wood parenchyma should show the most general distribution 

 of colouring substances. The fact that the xylem of D. 

 insignis is highly parenchymatous and is really white points 

 to the conclusion that for the production of ebony the 

 superabundance of colouring material is the first desideratum, 

 rather than profusely pitted elements. An open type of pit 

 communication between the elements will tend to prevent 

 the formation of central ebony in timbers where the colouring 



