THE ANATOMY OF THE STEM OF THE BERBERIDACEYE. 
507 
10. Spines occur both, as epidermal outgrowths from the stem and as modified 
leaves. 
The Epimedese include Epiniedium, Yancouveria, and Nandina, and doubtfully 
also Jeffersonia and Achlys. With the exception of Nandina, none of the genera 
investigated are woody. 
Nandina domestica, Thunb., is a Japanese shrub. In the young stem there are 
distinct ridges formed by the development of sclerenchyma, especially in the 
neighbourhood of the vascular bundles. The vascular bundles are well separated 
by small cells which afterwards form medullary rays, 5-8 cells in width, in the 
older stages. The ridges gradually disappear owing to the development of scler- 
enchyma levelling up the depressions. The four or five large vascular bundles have 
rather smaller ones alternating with them, but all traces of this distinction disappear 
in older stems. 
When in the young state the phloem areas are distinctly rounded in section and 
are destitute of lignified fibres. The xylem consists mainly of vessels with wide 
lumina, together with a few parenchymatous cells, while simple pitted fibres border 
the medullary rays, as in Berberis. The vessels show a variety of markings : spiral 
in the protoxylem, in other parts reticulate ; slit-like pits merging into reticulate 
and bordered pits with slit-like apertures. Occasionally tracheids with bordered 
pits are also present. 
When young most of the pith consists of thin-walled cells, but later it becomes 
entirely sclerotic. The pith is relatively large, comprising about 80 per cent, of 
the area in the transverse section of an old stem. Some of the cells are elongated 
and show simple pits ; they appear to act as storage organs. Some near the 
periphery show peculiar forked endings. 
Vancouveria hexandra, C. Morr. and Dec. — The species possesses an underground 
stem or rhizome in addition to the normal aerial stem. 
The aerial region in the young state has a slightly cutinised epidermis followed 
by two or three rows of cells which are elongated longitudinally and show no inter- 
cellular spaces. Next follow three or four rows of small sclerotic fibrous cells forming 
a distinct ring, but merging into larger thin-walled cortical parenchyma, as a rule 
devoid of contents. Through this tissue run widely separated vascular bundles. In 
the young condition more than half of the bundle is composed of phloem without 
fibres. The xylem consists entirely of spiral and pitted vessels with comparatively 
wide lumina, while the protoxylem is flanked by small sclerotic cells in older stems. 
The xylem of the vascular bundles in the rhizomic region is so embedded in 
sclerotic tissue that together they form a complete ring of stereome, except in some 
old specimens where the continuity is interrupted and the internal and external 
parenchymatous areas are united by broad bands of non-sclerotic tissue. The 
phloem occurs in patches outside the stereome ring, and consists mainly of sieve 
tubes and companion cells. The sieve plates are in some cases transverse, in others 
