THE ANATOMY OF THE STEM OF THE BERBERIDACEH3. 
509 
protoxylem are spirally thickened, the others have reticulate or bordered slit-like 
apertures. 
4. Prosenehymatous fibres occur only in Nandina and in the rhizome of Van- 
couveria ; in the other genera xylem parenchyma replaces fibres. 
5. Except in Nandina and in the rhizome of Vancouveria the bundles remain 
isolated, and the interfascicular tissue is unlignified. 
6. The central parenchyma in Nandina becomes sclerotic, but in Vancouveria 
and Epimedium only the cells in close proximity to the protoxylem show sclerosis. 
In all save Nandina the cortex tends to become lacunar. 
7. The vascular bundles are arranged in a ring, although developmentally con- 
structed from two rings interlocking. 
Achlys trijphylla, DC. — In the aerial stem the bundles are irregularly arranged 
(fig. 13), and only a few are in contact with the ring of sclerotic tissue, which is 
similar in position to that in Vancouveria, Epimedium, and Jeffersonia. The smallest 
bundles are toward the periphery and the largest ones toward the centre, but no 
definite arrangement in rings is observable. The general appearance recalls the 
arrangement in Podophyllum rather than that in the Epimedese. 
The xylem consists chiefly of spiral vessels without fibrous elements. The 
phloem is rounded in section and consists of sieve tubes with occasional companion 
cells. The sieve tubes show sieve areas on their lateral walls. 
The bundles in the rhizome are arranged in two rings, as noted by Tischler (9). 
The main bundles form an inner ring, while the others, which consist chiefly of 
sclerenchyma, alternate with them and are nearer the periphery. The cork cells 
resemble those of Berberis ; they have wide lumina, are deep-seated and of pericyclic 
origin. The xylem contains pitted vessels and tracheids. Pericyclic fibres do not 
occur in the rhizome. 
The Podophyllese include Podophyllum and Diphylleia, and also, according to 
Lotsy, Jeffersonia, Achlys, Hydrastis, and Glaucidium, although the two latter genera 
are placed by most' systematists in the Ranunculaceae. Podophyllum Emodi, Wall., 
very closely resemble P. peltatum in anatomical structure, as described by Holm (10). 
Stems of different ages show irregularly arranged bundles, widely separated 
from each other, the largest being central (fig. 14). With the exception of the 
cambium present in each bundle, the stem in section has the appearance of a 
normal Monocotyledon. 
In the bud stage no sclerosis is present in the cells surrounding the bundles, but 
later a crescentic mass of sclerenchyma arises on the phloem side. Towards the 
periphery there is a ring of sclerenchyma in which the phloem of the outer bundles 
is embedded, as in Epimedium and Jeffersonia. 
At first only a few of the xylem elements are lignified and show spiral markings, 
later formed units show annular and reticulate thickenings. Xylem parenchyma 
occurs but no fibres* The phloem appears to consist solely of sieve tubes with 
TRANS. ROY. SOC. EDIN., YOL. LII, PART III (NO, 19). 
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