138 Curtis . — The Anatomy of the Six Epiphytic 
A depth of about twenty cells in the cortex gives a parenchymatous 
appearance to the stem. There is no complete sclerenchymatous ring, 
but the outer vascular bundles have extended sheaths which may almost, if 
not actually, touch. The minute epidermis is bounded by a thick cuticle. 
The size of the cortical cells is greatest in the central region and diminishes 
towards either edge. Small intercellular spaces occur between the largest 
cells, which are oval in shape, and again between the small round cells 
of the innermost rows. Little marking is visible in any of the walls. What 
does occur is due chiefly to the occurrence of small pits. Raphides are 
present in the outer cortex. The phloem sheath of the central vascular 
strands is frequently four cells deep, and the walls of those of its fibres which 
adjoin the ground tissue are heavily pitted. The usual elements occur in 
the somewhat large strands of xylem and phloem. As a rule the vascular 
bundles are separated from one another by two rows of the large oval cells 
of the ground tissue. These have thick, heavily pitted, cellulose walls and 
contain great quantities of starch. 
The leaf sheath resembles that of E. mucronata , but is firmer 
in every way (PI. IX, Fig. 39). Nearly all the large sclerenchyma strands 
enclose vascular bundles. The cuticle is thick, especially on the outer 
epidermis. Pits are wide and numerous in the general tissue, particularly 
in the reticulately marked cells near the canals. The vascular sheaths con- 
tain many small fibres, but at the junction of xylem and phloem their 
elements are larger and have thinner walls. 
In the branch a great number of vascular bundles occur throughout the 
cutinized ground tissue. A heavy cuticle is present. The cells of the four- 
to five-rowed cortex are elongated in longitudinal section and may contain 
a little chlorophyll, while the ground tissue is filled with tetrahedrally 
arranged starch granules. The vascular elements resemble those of the 
stem. At the centre of the branch the sheaths do not extend round the 
xylem. 
In the leaf the two halves are practically in the same plane, but 
the edge may be slightly recurved. There are usually twenty-three 
vascular bundles, and of these five are large. Small sclerenchymatous 
strands run parallel to the leaf surface immediately within the two epidermes, 
but they are not as large, nor proportionately as numerous, as in the leaf of 
E . mucronata. The group of fibres at the edge of the leaf lies close to the 
lower epidermis. There is a distinct furrow above the midrib and a slight 
one above each of the other large vascular bundles. The cells of three or 
four rows near the upper epidermis are arranged in palisade formation. 
The walls are thin and pitted, the protoplasmic contents vacuolated, and 
fewer chlorophyll granules are present here than elsewhere. This resem- 
blance to water-storing tissue is more noticeable in the cells lying over the 
midrib. The elements of the epidermis are regular in shape. Their walls 
