4 МВ. W. RUSHTON : STRUCTURE OF THE 
pits a smaller number of rims was demonstrable. Finally in J. communis, 
which shows the smallest number of pits per tracheid, it was only possible to 
demonstrate an average of one rim for every eight tracheids. 
| Medullary Rays. 
The rays in all four of the Indian species agree with those of the American 
in being mostly uniseriate, occasionally biseriate in tangential sections, 
with the cells round, oval, or oblong in outline, and made up entirely of 
thick-walled parenchyma with simple pits in their upper and lower walls, 
and half-bordered ones on their lateral walls, 1-4 per wood-tracheid in the 
spring and summer wood of the various species. Where only 1-2 pits 
per wood-tracheid occur, they are arranged in a single radial row, but 
where more occur, in two radial rows one above the other. Often in the 
summer wood the ray-cells widen out parallel to the long axis of the stem 
and three pits occur one above the other per summer-wood tracheid 
(fig. 12). The end-walls of the ray-cells are coarsely pitted in tangential 
sections, giving the appearance of a network of end-wall interspersed with 
irregular-shaped pits. The length of the cells is equal to the width of 4-8 
spring-wood tracheids and 3-6 summer tracheids radially. Frequently in 
the summer-wood zone the ray-cells are much shortened and widened out 
parallel to the axis of the stem and often dovetail into each other. 
The height of the rays seen tangentialy varies from 1-20 cells in 
J. communis, 1-18 in J. macropoda, 1-12 т J. Wallichiana, and 1-8 in 
J. recurva. 
Resin Cells. 
Resin cells occur in all four species, but in different areas of the growth- 
ring. In J. recurva they sometimes occur in a definite zone in the early 
summer wood, but more frequently they are scattered throughout the late 
spring and early summer wood, but never extend outwards beyond the third 
tangential row of summer tracheids from the outer limit of the year’s growth. 
In J. macropoda, J. Wallichiana, and J. communis, they occur in definite 
zones, but the position of the zone varies. In J. macropoda the cells occur 
up to the outer limit of the growth-ring and never more than 4-6 tracheids 
away from it, often also occurring in the early spring wood of the following 
year’s growth. In J. Wallichiana the resin zone is more often in the middle 
of the growth-ring and extends up to a limit of six tracheids from the outer 
boundary, whereas in J. communis the zone is more constantly in the middle 
of the growth-ring and never extends nearer than 20-25 tracheids from the 
limit of the year’s growth. The length and width of the resin cells also 
vary, being shortest in J. macropoda, 65-88 и long with a width of 3-5 u 
radially and 16 р tangentially, intermediate in J. recurva and J. communis, 
125-200 р long and 12-15 и wide radially, and greatest in J. Wallichiana, 
