THE ANATOMY OF THE STEM OF THE CALYCANTHACEHd]. 
525 
glandular cells occur, but they are not nearly so numerous as in Calycanthus. The 
cells of the innermost layer of the parenchyma contain abundant starch grains, and 
represent an endodermis, though in other respects they do not differ from the outer- 
lying cells. The endodermis surrounds the outer border of the peripheral bundles, 
leaving no doubt as to their pericyclic origin, though Lignier regards them as 
cortical. The peripheral bundles are elliptical in outline, and consist of an internal 
phloem followed externally by xylem, and a mass of sclerenchyma. The phloem is 
well developed, but does not form wings as in Calycanthus. The xylem is poorly 
developed. It consists entirely of annular, spiral, and reticulate vessels and a few 
spiral tracheides, there being no xylem parenchyma. Double spirals occur both in 
the vessels and the tracheides. The pericyclic layer consists of isolated groups of 
uniformly sclerotic fibres, situated immediately inside the endodermis. Cells with 
irregular thickenings are rarely seen in a first-year stem. Occasionally glandular 
cells are found in between the cortical stele and peripheral bundles. The phloem 
consists almost entirely of parenchyma, sieve-tubes and companion cells being few 
in number. Frequently, on the inner sides of the parenchyma cells bordering the 
inner margin of the peripheral bundles, radial foldings occur, usually extending about 
half way across the cell. Glandular cells are frequent in the bast, and the cambial 
layer is barely distinguishable. In the older parts tracheides with multiseriate 
bordered pits are found, but the pits are only faintly developed. Abutting on the 
protoxylem is a small-celled chlorophylliferous pith, merging into a central large- 
celled colourless pith. Oleiferous cells are found towards the periphery, but are 
rare, though Van Tieghem states that they do not occur in the pith. Medullary rays 
are uniseriate and resemble closely those found in Calycanthus. 
The pericyclic ring in stems two or more years old is completed by irregularly 
thickened sclerotic cells which fill up the gaps between uniformly sclerotic fibres, 
while the secondary xylem consists mainly of lignified fibres in which the tracheides 
are embedded. The commonest type of tracheide is that with bordered pits and 
spiral or reticulate markings, while tyloses are often found partly blocking their 
lumina. Xylem parenchyma is of rare occurrence in the old wood, though it is 
fairly abundant in the younger tissues. 
The leaf-trace insertion differs slightly from that occurring in Calycanthus. 
There are three foliar vascular bundles, one large median, and two smaller lateral. 
Two gaps are formed on opposite sides of the vascular ring of the axis (a) imme- 
diately above the point of insertion of the petiole. Two buds are seen in the 
axil ; the inner is large, the outer very small. At a lower level the inner bud 
receives a strand from the peripheral bundle of the axis ( b ), and the vascular tissue 
of the axillary buds arranges itself into two semicircles on either side. These fuse 
by their adjacent ends. A gap occurs first on the inner side, then on the outer side, 
and each half fuses with the vascular tissue of the central axis. Meanwhile, the 
peripheral bundles become elongated tangentially, and receive the lateral foliars as 
TRANS. ROY. SOC. EDIN., VOL. fill, PART III (NO. 20). 80 
