AND HISTOLOGY OF PIPER BETLE, 373 
the very early differentiation of the vascular strands. They are ranged in 
two distinct rings. The inner one lies within the circle of mucilage-canals 
in the medulla. These are the medullary vascular bundles ; they vary in 
number usually from six to twelve. When their number is small they form 
one irregular circle in the ground-tissue, so that the ring becomes sinuate, but 
not distinetly double. They vary in size, especially when they are numerous, 
and then those that are crowded out are smaller than the inner ones; nor are 
they in such a case evenly spaced, ах some of them get too close to each 
other. The bundles are collateral in tvpe; they are usually normally 
orientatel. However, when their number is large, the outer ones may be 
twisted out of the normal position through an angle of 90°, so that the line 
between the xylem and phloem comes to be a radius instead of being a 
tangent. In shape they are almost circular at this stage. There is not any 
strict relation between the vascular bundles and the mucilage-canals either 
as regards number or as regards position; however, in some sections a 
mucilage-canal is observed in all the radii occupied by the crowded-out 
bundles. Lignification of the annular and spiral vessels has been observed 
within a hundred microns of the apex. The pith is limited by a sinuate zone 
of cells which are destined to form a sclerenchymatous ring. It is clearly 
indicated in sections from near the apex by the smaller size оЁ the cells; but, 
unlike the vessels, they are not sclerosed at this early stage. It is about four 
to five cells deep. The peripheral vascular bundles are directly applied to 
this ring. They are very unequal in size, There are about five or six large 
bundles approximately equidistant from one another. They project pro- 
minently out of the circle of the remaining bundles towards the pith, and push 
the sclerenchymatous ring inwards in so doing : hence the latter is thrown 
into deep sinuations. Besides the larger bundles there is a variable number 
of small bundles, from 12 to 24 or more. Many of these appear in the 
transverse section as tiny specks. Some of the smaller bundles that are 
comparatively large project slightly inwards so as to produce gentle 
undulations in the fibrous ring. АП these bundles constituting the peri- 
pheral ring are strictly normally orientated. 
The spaces between the bundles are occupied by parenchymatous cells ; 
these differ from similar cells of the pith in their smaller size and greater 
closeness. Outside the ring there is a narrow pericyclie zone, about five cells 
deep, of parenchyma, which agrees with that of the medulla. It is bounded 
externally by the single complete circle of endodermal cells. "The radial 
walls show the characteristic cog-like thickening. Their contents are marked 
by the presence of starch-grains. 
The cortex outside the endodermis is characterized by particular abundance 
of secretory cells within it. It also contains collenchyma, which is in the 
form of isolated ares separated by broad radii of parenchyma, which are, as it 
were, ties connecting the parenchyma lying on either side of the collenchyma- 
LINN. JOURN.—BOTANY, VOL. XLI. op 
