THE ANATOMY OF THE STEM OF THE CALYCANTHACEiE. 
521 
selves crescentwise, each joining the adjacent margin of the median bundle, thus 
forming a more or less continuous arc. This gradually approaches, and finally 
becomes inserted in, the central cylinder. Before doing so, however, the median 
foliar bundle gives off two lateral strands, one on either side. Each lateral strand 
divides into two segments, one of which joins the lateral foliar bundle, the other 
unites with the peripheral bundle of the axis. The lateral foliar bundle joins the 
peripheral bundle of the axis a little lower down, and has no connection with the 
central stele. Immediately after the median foliar bundle has joined the central 
cylinder and the laterals have united with the peripheral bundles, anastomosis takes 
place between the flanking- peripheral bundles. The vascular strands of the foliar 
bundles are normally orientated, but the lateral segments, on approaching the 
peripheral bundles of the stem, become inverted. The arc formed by the median 
on entering the stem becomes less and less conspicuous as the node merges into 
the internode below, where the central cylinder becomes cylindrical once more. 
The stem of Calycanthus jioridus shows very little difference in external appear- 
ance from that of C. fertilis. 
In transverse section it also resembles in all essential respects C. fertilis. The 
normal vascular bundles fuse to form a complete ring by an early development of 
an interfascicular cambium, leaving only narrow medullary rays between. These 
rays are only one cell wide, even in -the young stem, and contain chloroplasts. 
The cambium ring is very conspicuous and four or five layers in thickness. Both 
in the normal vascular ring and in the peripheral bundles, crystals of calcium 
oxalate are deposited in radiating masses, either attached to the cell membrane 
or lying free in the cells. Double spirals are often met with both in the protoxylem 
of the central stele and of the peripheral bundles. Tracheides with bordered pits 
occasionally occur in the primary xylem. The sieve-tubes are very indistinct in 
the central bundles, but are clearly differentiated in the phloem of the peripheral 
bundles. Companion cells with dense contents are very prominent. 
The secondary xylem consists mainly of reticulate tracheides with uni- or multi- 
seriate bordered pits, or with scalariform markings. The secondary xylem also 
includes lignified pitted parenchyma cells. Sanio (12) states that the walls of 
these cells become broken down by the disintegration of the membrane to form a 
mucilage or gelatinous layer which turns violet on treatment with iodine and bright 
crimson with phloroglucin and hydrochloric acid. As in C. fertilis , there are also 
lignified prosenchyma fibres without markings or pits, interspersed among the other 
elements, probably mechanical in function. 
The peripheral bundles in older stems are surrounded by a layer of slightly 
sclerotised cells. The collenchyma cells have thick walls with canal-like pits. 
The walls of the cortical cells are also thickened, but not to so great an extent. 
The pericycle consists of isolated groups of sclerotic fibres between the phloem of 
the central stele and the parenchymatous cortex. Between the groups some of 
