GEKTJS DIOSPYROS 
34 WRIGHT : THE 
of donble rays. In tracing one ray from the younger to the 
older wood it was first seen to be three cells broad, and very 
gradually one marginal row Was replaced by a row of fibres, 
and finally, the double ray passed into a single ray, each 
component having a tangential diameter equal to the sum of 
those forming the double ray. It has also been noticed in 
specimens of D. attenuata, that whenever the ray is more 
than one cell broad the component cells are invariably of 
the horizontal type, and at each end of such a ray the 
components are of the vertical type with large tangential 
It is to be noted that whenever the ray is more than one 
cell broad the components have always a small tangential and 
large radial diameter, and many sections show a double 
ray superposed on a broad single ray, each ray extending 
vertically through a distance of many cells. 
The medullary rays form large vertical strands of tissue 
from twelve to over thirty cells in height, the components 
having very variable dimensions and forming part of single, 
double, and triple rays. 
The medullary rays, since they pass throngh all the 
secondary rylem, comeinto direct communication with every 
other type of cells, but the most striking communication is 
with tte wood parenchymm which they so closely resemble 
tt*rtaonlarly the vertical type) in structure, thin walls and 
crowded contents. 
tionT tT C “ ^ tre * ted totter in 8 oom *>ined descrip¬ 
tion of the differentiation of medullary ray tissue. 
■tt d,ere * a 
—rr:anT^xrr a ; 
mtroduco^ yet another type having approxi^ttm 
