502 
R. J. HARVEY-GIBSON AND ELSIE HORSMAN ON 
developed as marginal outgrowths towards the apex of each leaf. The flowers 
are yellow and trimerous, suggesting an affinity with Monocotyledons. 
The most prominent feature shown in a transverse section of the stem is the 
deeply-seated ring of cork cells with remarkably large lumina. The tissues are 
arranged in the following sequence (figs, f , 2) : — ■ 
1. An epidermis of regular- rectangular cells with cuticle and numerous 
stomata. 
2. One or two layers of thin-walled cells with intercellular spaces. In older 
stems these cells persist in that condition, but in other cases they are crushed by 
the growth of tissues more centrally placed. 
3. These cells are bounded internally by a ring of sclerotic tissue three or 
four layers thick. In very young stems this ring is not quite continuous, but is 
interrupted by thin-walled cells, usually in the interfascicular regions, agreeing in 
this respect with the similar ring found in the Papaveracese (l). In older stems 
the sclerotic ring increases considerably in thickness and complete continuity is 
established, though later it is again segmented into patches as a result of the 
tension set up by the growth of the internal tissues and as a preliminary to being 
cast off by the cork. 
The individual fibres are long, and their endings are either truncate, oblique, 
or tapering. They all show simple pits. Occasionally this tissue, by hypertrophy, 
produces ridges, although other species show this to a much greater extent than 
B. vulgaris. Solereder considers this ring as belonging to the outer pericycle. 
4. Immediately within this sclerotic band is the deeply-seated cork, which at 
first consists of one layer of regular, large, thin-walled cells with remarkably wide 
lumina. These cells are two, three, or more layers deep in older stems. 
5. Next follows a region of cortical cells, the outer being small and compact, 
the inner larger and having intercellular spaces. All are thin-walled and have 
protoplasmic contents. In the medullary ray region, “berberin” is present in 
the form of yellowish-green granules, and often the whole cell contents are im- 
pregnated with it ; some cells in this region contain also klinorhombic crystals of 
calcium oxalate, which almost completely fill the cell lumina (fig. 3). Berberin is 
an isoquinoline alkaloid, insoluble in water, and hence can be best seen in sections 
of fresh material mounted in water. Spirit in which Berberis material has been 
preserved becomes yellowish-brown owing to the dissolved “ berberin,” which 
remains as a resinous deposit on evaporation. Further research is at present 
being carried out on the chemical composibion and reactions of this substance. 
According to Solereder, the fibrous ring, the cork, and the cortical region 
just mentioned form a composite pericycle. 
No endodermis is differentiated, for ordinary cells of the cortex abut directly 
on the vascular bundles. 
In the young stem the vascular bundles are distinct, the interfascicular regions 
