STRUCTURE.] MYZODENDRON. 217 



cells, as in most, if not all, the Loranthacese, at other times 

 they are in two series or variously disposed. This tissue does 

 not appear to pass from one internode to another, but to be 

 interrupted at each articulation, as M. Decaisne found to be 

 the case in Viscum. The parenchyma between the vessels of 

 the liber and wood is often dense; sometimes, but rarely, 

 these vessels are seen to be immediately in contact with the 

 wood. 



"Within the bark are arranged two concentric series of 

 woody plates or wedges ; these two series are separated by a 

 zone of cellular substance, and are generally arranged with 

 tolerable precision : besides these the pith of the plant is 

 intruded upon by other wedges or bundles of vascular tissue, 

 unsymmetrically disposed, one of them often occupying the 

 axis itself. Each wedge or plate is composed principally of 

 concentric layers of very large vasa scalariformia, becoming 

 more densely packed and much smaller in diameter towards 

 the axis of each layer, where they are almost invariably 

 furnished with a spiral filament. Between the layers of the 

 first three or five years there is generally deposited two 

 bundles of pleurenchyma similar to that of the liber, one on 

 each side, but between the more recent layers there intervenes 

 only the more delicate vascular tissue as mentioned above ; 

 however, pleurenchyma is sometimes more copiously deposited 

 between every layer. The narrow portion of each wedge 

 invariably rests on a mass of pleurenchyma deposited at the 

 same time as the fibres of the liber, that is during the first 

 year, as in the common Miseltoe. The wedges of wood 

 belonging to the second series are smaller than those of the 

 first, but similarly formed in all respects, and consisting of 

 as many layers, though the inner are very inconspicuous. 



" The pith consists of cellular tissue similar to that of the 

 liber, and is very lax even in the older stems. 



" The transverse section of this stem appears at first sight to 

 differ very remarkably from that of most exogenous plants ; 

 this arises from the wood being deposited in two concentric 

 series, separated by a broad zone of parenchyma, from the 

 great breadth of the medullary rays, the irregular distribution 

 of the fibres of the liber which are sometimes biserial, and 



