THE ANATOMY OF THE STEM OF THE BERBERIDACEH3. 
505 
The sclerotic pericycle in some cases is increased so much as to form ridges in 
the stem, e.g. in B. angulosa, Wall. (fig. 8), and B. Yunnanensis, Franch. 
The spines so characteristic of the Berberidaceae consist mainly of sclerenchy- 
matous fibres and are obviously modified leaves, as shown by their position at the 
nodes and by their structure. The sheath of sclerenchyma almost entirely encloses 
two cavities filled with loosely arranged thin-walled cells and one or more vascular 
bundles (fig. 9). Stomata are found only on the incurved surface, where they are 
abundant. The sclerotic fibres are continuous throughout the spine to the tip, which 
is formed solely of fibres covered by epidermis. 
The inner layers of the heterogeneous pericycle, which consist of thin-walled 
parenchyma, are often so loosely arranged as to produce conspicuous cavities crossed 
by cellular bridges (fig. 10). In some species these layers are increased locally, 
contributing to the production of the stem ridges. 
Resin ducts are present in the phloem in some cases. In transverse section they 
appear to consist of single large cells with lignified walls showing oval pits (fig. 11). 
In the young stem of B. Jamesoni, Lindl., vessels and tracheids with com- 
paratively large lumina predominate, but as the stem increases in age and girth 
lignified fibres -are developed bordering the medullary rays, as in B. vulgaris. 
According to Haberlandt (11), “medullary rays always abut directly against 
xylem parenchyma on their flanks as well as on their upper and lower borders.” 
This suggests that the prosenchymatous fibres which always border the medullary 
rays may be parenchyma cells modified to give additional support to the stem 
(fig. 12). They are well supplied with simple pits, while some show septa and many 
contain starch grains. 
Several species show oval bordered pits longer than those of B. vulgaris, e.g. 
B. Sieboldii, Miq. Others show bordered pits in conjunction with faint reticulate 
markings, e.g. B. Wallichiana, DC., and B. Yunnanensis, Franch. The former 
also shows loose reticulate markings in vessels without pits. 
A few species show a slight development of normal xylem parenchyma, e.g. 
B. stenojphylla x hort., B. Jamesoni, Lindl., B. Sieboldii, Miq. The parenchyma 
when present always surrounds the larger vessels in the protoxylem regions, and is 
usually lignified and similar to the xylem fibres in transverse section. 
In B. angulosa, Wall., the greater portion of the wood consists of tracheids with 
round bordered pits resembling those of Pinus, but smaller in size. 
Solereder states that scalariform markings occur occasionally in Berberis ; no 
such thickenings were found in any of the species of Berberis examined, though 
they are to be found in Podophyllum and Diphylleia. 
There is very little variation in the medullary rays ; most of them closely 
resemble those of B. vulgaris. The ray cells are well lignified, thus rendering them 
hardly distinguishable from the surrounding xylem. They vary in width from two 
to eight cells, the widest being found in B. Wallichiana, DC., where they have 
