INTRODUCTION 11 
formation, which leaves the inner cortex intact even in 
old stems. 
Two kinds of specialized elements occur in this layer, 
The first are small cells set aside for the purpose of con- 
taining crystals of calcium oxalate. These cells are only 
found in older stems, and are very frequent in the neighbour- 
hood of cankers. The second are irregularly branched 
sclerenchymatous cells with 
very thick walls (fig. 6, s.e.). 
These elements grow longi- 
tudinally, forcing their way 
between the parenchymatous 
cells, and often branch. The 
branching occurs when a 
sclerenchymatous cell en- 
counters a parenchymatous 
cell broadside, and one branch 
grows down on each side of 
the obstructing cell. The 
function of these cells. is 
obscure. 
There is no distinction be- 
tween the cortex and pericycle, 
but in the parenchyma im- 
mediately abutting on the 
phloem (and thus presumably a 
pericycle) there are here and a 6.—Longitudinal section of 
: phloem: c.c., crystal-containing 
there large intercellular spaces cell; m.r., medullary ray; p.p., 
which contain resin. When phloem parenchyma; s.e., scleren- 
chymatous clement;  s.t., sieve 
young they are small and tube (x 420). 
spherical, but with the in- 
creased girth of the stem they become laterally extended 
and are conspicuous objects in all sections ; they also acquire 
a poorly developed epithelium. They appear to be associated 
with some of the larger medullary rays, which, when followed 
into the xylem, are found to be in contact with resin ducts 
in the first-year wood. 
The phloem is composed of sieve tubes, crystal-containing 
foxe\= 
Og eSag 
Wine 
