ANATOMY OF THE JULIANIACEEX. 141 
system and the closure of the gap in the vascular ring of the stem. The arrangement 
of the bundles in the detached petiolar system is very much like that found at the base 
of the petiole, the open upper end of the vascular are corresponding in position to the 
gap in the axial vascular ring, but not being quite so pronounced as it is at a slightly 
higher level. Resin-canals seem to bend out into the petiole with the bundles. 
The gap in the vascular ring of the stem caused by the emergence of the petiolar 
system is persistent even during the subsequent growth in thickness. In the young 
condition it is occupied by parenchymatous tissue, which has passed into it from the pith 
to take the place of the outgoing vascular tissue. In the older parts of the branch, some 
way behind the apex, these gaps in a transverse section appear as broad medullary rays 
composed of cells with somewhat thickened walls and bearing simple pits with a reticulate 
arrangement; these broad rays traverse a thick band of secondary wood, and are situated 
opposite the persistent leaf-bases, which, as will be remembered, are adnate for some 
little distance to the stem. The vascular system in these persistent leaf-bases also 
undergoes a certain amount of growth in thickness; successive sections through such a 
leaf-base enable one again to follow up the gradual bulging out of the petiolar system 
from the vascular ring of the stem and its final detachment. In the upper portion of 
the persistent leaf-base, however, the secondary wood and phloem of the vascular tissue 
form a complete ring. 
(ii. THE STEM. 
The structure of the stem is very constant in all the members of the Order, although 
distinguishing features are in some cases afforded by the distribution of the resin-canals. 
The common occurrence of isolated sclerenchymatous cells in the primary cortex is 
noteworthy as being the only indication in the vegetative organs of the plant of that 
tendency to form sclerenchyma which is so abundantly exhibited by the fruit. 
The origin of the cork is apparently subepidermal, although it was not possible to 
determine this point with absolute certainty. The cells of the cork in most cases have 
relatively thin walls and are tabular in shape; the outer tangential walls are slightly 
arched outwards, whilst the radial walls are more or less undulated; in herbarium 
material the cells are commonly filled with tannin. In Juliania glauca the inner 
tangential walls are very considerably thickened. In longitudinal sections the cork-cells 
appear tubular and somewhat elongated. | 
In many cases a considerable number of the cells of the thin-walled parenchymatous 
primary cortex subsequently become more or less strongly thickened and sclerosed ; 
this phenomenon is wanting only in J. glauca, where possibly the thickened cork-cells 
make up for the lack of sclerosis in the primary cortex. In the other species one 
frequently finds all stages from slightly thickened cortical cells with a wide lumen to 
stone-cells with a very small cavity. The thick walls of these cells are traversed by 
simple pits, which, however, sometimes appear to be bordered, owing to the dilatation 
of the pit-passage inside the substance of the wall. These thick-walled cells are all 
isodiametric or only very slightly elongated in the vertical direction. In J. amplifolia the 
entire inner portion of the primary cortex is composed of somewhat thickened and pitted 
