STRUCTURE. 5 1 



cut transversely, with xylein inside and phloem next the cortex ; their 

 origin or end I was unable to learn. On the surface of the stem at 

 each node or point of union of a petiole with the caudex, there is in 

 N. flava a prominent conical projection, on the upper face of which 

 the petiole is attached, and on the lower face the roots. Within the 

 tissues of this projection the bundles from the attached roots unite 

 into a single trace, and this passes horizontally through the cortex to 

 the lower edge of the leaf-gap. A few cells join the vascular cylinder 

 of the stem directly, but most of the trace is contained in two large 

 lateral forks, one right and one left, which start almost horizontally 

 into the vascular cylinder and could not be followed. The petiolar 



FIG. 33. Course of vascular bundles at node of JV)/j>h<ir.i tlnr<i. nn Must 1 of petiole ; <M hasp of peduncle; g, leaf 

 sap; rr, roots; u, vascular cylinder of stem, semi-diagrammatic; (<) diagrammatic projection of (a); p, petiole. 



bundles are nine in number, three in a median vertical plane, and six 

 smaller lateral ones. Of the first three, one is anterior, one median, 

 and one posterior. The others are right and left antero- and postero- 

 lateral, with one directly right and one left of the centre of the petiole. 

 On entering the stem, the posterior and median bundles fuse, and 

 are shortly joined by the anterior, the whole forming a large central 

 leaf-trace. The right and left antero-lateral bundles are joined at about 

 the same level as the above, by the directly right and left bundles, and 

 the two fused bundles then join the central leaf-trace. This trace passes 

 horizontally in through the cortex and comes in contact with the root- 

 trace, then passes over the brink of the leaf-gap and turns sharply down- 

 ward next to the pith, giving the appearance noted in the cross-section. 

 About midway on its course through the cortex, the central leaf-trace 



