304 CALAMAR1EAE. 



small extent, show that still greater deviations occur in the nodes (Fig. 41 5), 

 and that by repeated formation of intermediate cauline strands from the upper 

 and possibly from the lower extremities of the primary rays, other elliptical 

 portions of the kind bounded, by loops of wood may be cut off. Such com- 

 plications, unknown as yet in the nodal zone of Equisetae, are extremely 

 common in Angiosperms, in which according to present observations they 

 cannot at all be referred to distinct types, but seem to be absolutely irregular. 

 In many cases, not indeed necessarily in all, these small meshes are traversed 

 by bundle-strands passing outwards (leaf-traces or traces of adventitious 

 roots), the transverse sections of which lie in the middle of their parenchyma ; 

 this has been already recognised and described by Williamson. The lateral 

 shoots also, where they traverse the wood, are seen to be surrounded by 

 similar strand loops l . Where the primary rays of Williamson's lower in- 

 ternode end above towards the zigzag strand of the node, the tangential 

 section very commonly shows in each of them a roundish or ovoid empty 



FIG. 41. Tangential section through the wood of Arthropitys, showing the irregularities of its course in the node 

 as mentioned in the text; at a the so-called infranodal canals. In some of the small rhombic nodal medullary rays 

 are transverse sections of vascular bundle-strands running towards the outside and indicated by points. After 

 Williamson (I). 



space with tolerably distinct boundary lines (Fig. 41), which, as appears 

 from some preparations in Williamson's collection, passes from within out- 

 wards through the whole length of the medullary ray 2 . These peculiar 

 canals, called by Williamson infranodal canals, are proved by other sections 

 in the same collection to be caused by the disappearance of a strip of paren- 

 chyma, which differs a little in character from the surrounding parenchyma 

 of the ray. Then in many cases the terminal segment which conceals the 

 canal is separated by formation of anastomoses from the internodal portion 

 of the ray, and is changed into one of the previously mentioned nodal 

 lacunae. We should accordingly have to distinguish two kinds of these 

 nodal rays, one containing the infranodal canals arranged in a regular circle 

 but no bundle-strands, the other, with much less regularity of development 

 in number and position, inclosing the bases of the branches, and in some cases 

 allowing other casual trace-bundles to pass through them. Williamson 

 places the latter exactly on the line of the node, the former beneath it. 



Williamson (1), IX, t. 21, f. 28. 2 Williamson (1), I, t. 26, f. 23. 



