320 Transactions. — Botany. 



These parallel cells contain a minute amount of chlorophyll, and are in 

 shape cylindrical, their average length being about five times the diameter ; 

 but the boundary of the cell-wall, which could not be traced in the cortical 

 tissue, is here occasionally clearly distinguishable in transverse section. 



hiternodes. — The internodes, which are in the early state semi-trans- 

 parent, become olive-brown when mature ; and the cavity which is 

 invariably found in them contains a saline solution. This central cavity 

 is to be detected in even the very young stages of their growth, when they 

 are no more than '03 inch in diameter. The only exception to the above is 

 the basal internode, which is solid throughout, but the one next above has 

 a small hollow centre, and the third, and sometimes fourth, is furnished 

 with a nearly full-sized cavity (PI. XIV., fig. 6). 



A few central threads, extending from the base to the top, may be seen 

 by splitting open a fi-esh internode. Their structure somewhat resembles 

 that of the nodes, the same thin layer of outer tissue being present, and 

 within this also the minute oblong cells of the limiting tissue (PI. XIII., 

 figs. 4 and 6). The cortical tissue, however, differs slightly from that in 

 the node, the cells being if anything more compact, though more irregular 

 in outline. 



Between the cortical and innermost tissue lies a mass of cells joined 

 together endwise, and forming long strings branching frequently, and 

 without any apparent uniformity (PI. XIII., figs. 4 and 6). These cells 

 are tubular and mostly straight, but at times curved and bent at various 

 angles. In some cases two adjacent rows of cells will be connected by a 

 short tube, with a septum midway, reminding one most forcibly of the 

 conjugation of Sjnrogyra. 



The innermost tissue of the internode is a collection of parallel rows of 

 cylindrical cells (PI. XIII., figs. 4 and 5), somewhat akin to the previous 

 layer, which in structure resembles this innermost tissue. 



All these tissues, though described as different layers, must not be 

 supposed to have a strong line of demarcation between them. On the 

 contrary, they blend almost imperceptibly into each other, with the excep- 

 tion of the limiting tissue, which is moderately well-defined, and the outer 

 single layer of polygonal cells. Owing to the thickness and gelatinous 

 nature of the cell-walls in the cortical and inner tissues, the cells unite to 

 form a transparent medium, the cavities in which are the only guide as to 

 the size and shape of the original components of the structure. 



As regards the connection between the different tissues in the node and 

 internode, it may be remarked that the outer single layer is continuous, also 

 the limiting and cortical tissues (PL XIII., fig. 6) ; but the layer of parallel 

 cells divides into two equal parts (as seen in longitudinal section) on leaving 



