54 WRIGHT : THE GENUS DIOSPYROS 



substance, and also that the disappearance of many grains is 

 due to their conversion into sugar for uses within the plant, 

 and may not be associated with the coloured globules under 

 consideration. If one examines the vessels of the sapwood one 

 often finds the globular material entering through the pits. 

 In one section the stream of coloured material could be 

 traced from the medullary ray cells through the pits into the 

 lumen of the wide vessel with which they were in contact. 

 In very many cases the coloured substances project into the 

 lumen of the vessel as large globules suggesting tyloses ; 

 these swell, and are partially soluble in water. The globules 

 may exhibit stratification according to the colour of the 

 different parts. 



In other cases the large globules are entirely absent, and the 

 deposit appears as a thin film of a pale straw-coloured material 

 in the area of the pits. The whole of the pits in the wall of 

 any particular vessel do not usually present this appearance, 

 the pits thus coloured usually occurring only in local groups 

 along the wall of the vessel. The deposit may become very 

 abundant, and when half filling the vessel is irregularly 

 globular in outline. It therefore appears that the material 

 occurring in the tracheal elements is derived from the 

 substances stored in the parenchymatous elements, and the 

 relative freedom of the latter from contents a feature often 

 noticeable in mature ebony may be a consequence of 

 exhaustion of store material. The infiltrating material may 

 be of a pale straw or light brown colour ; as it increases in 

 quantity the tint deepens and the elements finally become 

 blocked with deep brown or black material. 



The gum-resin issues in large quantities from the stumps of 

 freshly felled trees and accumulates at points of exposure. 

 The walls of the elements from trees which have yielded 

 large quantities of this substance do not show any reduction 

 in thickness, and it is probable that they have been derived 

 from disintegration of store materials in the parenchyma of 

 the wood. 



