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 vessel s 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. 
