WRIGHT : THE GENUS DIOSPYROS 
of measurements of transverse dimensions of the fibres in 
the sapwood and heartwood is given below 
The above table would perhaps lead one to believe that 
our wet country species had generally larger transverse 
dimensions than our dry zone species. It is also to be noticed 
that there is not, in every case, an increase in transverse 
dimensions as one passes into the sapwood, and that 
the maximum variation in transverse dimensions for the 
fibres in the whole of our species is about 0*006 mm. and for 
fibres of the same species less than half this amount. 
The transverse dimensions, thickness of wall, &c., may 
be greatly modified by individual forces, stress, windage, 
Ac. 
Medullary Rays .—These elements are, as far as the genus 
Diospyros is concerned, the most variable of all the com¬ 
ponents of the secondary xylem. Fundamentally they are 
similar to the wood parenchyma cells since they possess 
thin cellulose walls and contain abundance of starch, tannin, 
and oxalate of lime. Their presence in abundance tends to 
lower the value of the timber, their thin walls and wide 
lumina rendering shrinking more certain. 
