THE ANATOMY OF THE STEM OF THE BERBERIDACEiE. 
503 
being composed of sclerotic tissue ; but later the bundles, together with the broad 
primary medullary rays, form a complete ring of lignified tissue (fig. l). 
The phloem consists of very small elements arranged in radial rows. In older 
stems it shows sieve tubes with bevelled ends occupied by sieve plates and callus, 
with slime strings across the plugs from segment to segment ; but no grouping 
of sieve plates into areas is observable. This may be due to the very small size 
of the sieve tubes, which also prevents the definite location of plates on the lateral 
walls, though they appear to be present. Some of the sieve tubes are accompanied 
by companion cells, although this is by no means an invariable rule. Phloem 
parenchyma is abundant, and the cells show intercellular communications. Ligni- 
fied fibres with deep simple pits are also present. They are short and spindle- 
shaped, and in cross section show strongly thickened walls and ■ small lumina. 
thus differing from the pericycle fibres, which are much wider and have walls less 
strongly lignified. These bast fibres are formed in tangential rows in the inner 
secondary phloem and border the lamellae into which the phloem is divided as 
growth proceeds, thus recalling the alternating bands of Vitis, though they are 
developed to a much less extent. A few scattered fibres are also -found in the 
outer primary phloem, but no stone cells are present. 
Crystals and “berberin” granules are found in the medullary ray region of 
the bast, as above mentioned. The bast fibres are not continued across these 
regions. 
In the. early stages the xylem elements are regular and similar in size and shape, 
with w T ide lumina, some showing remains of protoplasmic contents. Later the 
lignification becomes more pronounced, the lumina decrease, and the arrangement 
in radial rows becomes more obvious. Comparatively large polygonal vessels are 
distinguishable in the protoxylem and in groups towards the centre of each 
vascular bundle. In the protoxylem the first formed vessels are spirally thickened, 
the innermost spirals being right-handed and later ones left-handed, as pointed out 
by De Bary (6). The other vessels possess bordered pits with slit-like apertures 
(fig. 5), the slits lying at right angles to the axis of the vessel ; many have 
faint spiral thickenings in addition to pits, similar to those recorded for Romney a 
(Papaveraceae) (l) and for Dendromecon by Leger (7). Most of the xylem consists 
of prosenchymatous fibres with simple pits on all their walls and often containing 
starch, particularly in the winter condition. These fibres always occupy the 
regions abutting on the medullary rays. Sanio (8) says that septate fibrous cells 
are found only in the first annual ring. This does not seem to be invariably true, 
although the septa are not so frequent in the fibres of the second and subsequent 
years. Comparatively few tracheids are present, and these have bordered pits 
accompanied by spiral thickenings, as in Taxus. There seems to be little difference 
between the pitted fibres and the pitted tracheids. Spiral tracheids resembling- 
fibres are also present. 
