508 
R. J. HARVEY-GIBSON AND ELSIE HORSMAN ON 
oblique, while some show sieve plates on their external walls. No lignified fibres 
occur. The vessels occupying the centre of the bundles show various forms of 
lignification — spiral, reticulate, or bordered slits. On the lateral borders of these 
groups of vessels are thickened prosenchymatous fibres which occupy the whole of 
the interfascicular regions, thus completing the ring of mechanical tissue. 
Outside the phloem areas are occasional sclerotic cells among the ordinary cortical 
cells, and beyond these lies a ring of slightly thickened cells corresponding to the 
sclerotic ring in the aerial stem. The rhizome thus contains two concentric rings of 
mechanical tissue — an inner one consisting of the xylem of the vascular bundles and 
sclerotic fibres, and an outer of sclerotic tissue only. The epidermal cells are thin- 
walled, and the sub-epidermal tissue consists of fairly large and irregular cells, many 
of which contain a brown deposit. 
All the material examined w r as herbaceous and showed no signs of any develop- 
ment of cork. 
Epimedium alpinum, L., shows a structure very similar to that of Vancouveria, 
but some of the vascular bundles are more peripheral, so that their phloems are 
embedded in the peripheral sclerotic ring. The medulla is markedly fistular. 
Many of the cortical cells are elongated with large oval pits in their walls, and 
hence are probably conductive. 
In the rhizome the ring of mechanical tissue is incomplete, the bundles being 
separated by broad plates of parenchyma. In the aerial stem there are two rings 
of vascular bundles. 
Epimedium sagittatum agrees with Vancouveria so far as the structure of the 
aerial stem is concerned. 
Jeffersonia dubia, Benth. and Hook., and Jeffersonia binata, Bart., agree with the 
three previous genera in having their vascular bundles arranged in a ring, some of 
them partially embedded in the ring of sclerenchyma ; in the structure of the xylem 
— having vessels with bordered slit-like pits, in having a lacunar cortex, and in having 
a phloem very rounded in section. In Jejfersonia dubia the sieve tubes are well 
developed, with well-marked callus plugs and faint canals across the callus, and the 
nodes on the median lamella. Solereder says the arrangement of bundles in 
Jeffersonia is Monocotyledonous ; but, apart from the fact that some bundles are 
smaller and rather nearer the periphery than others, the material we have examined 
presents no evidence in support of this statement. 
The chief characters of stem anatomy of Bpimedese may be summarised as 
follows : — 
1. There is a continuous ring of sclerenchyma, pericyclic in origin. 
2. The phloem bundles are very rounded in outline and have no fibres. The 
sieve tubes are larger than in Berberis, and in many cases show sieve plates on the 
lateral walls. 
3. The xylem consists chiefly of vessels with fairly wide lumina. Those of the 
