Notes . 
77 5 
observations made upon the stems of E. Telmateja , &c., show that this 
comparison cannot be satisfactorily maintained. 
It was fpund that of the three strands of xylem present in each 
bundle of the internode, the carinal strand alone passes out at the 
node as a leaf-trace. The two lateral strands join on to the xylem of 
the nodal ring, and in certain species (E. hiemale , and better still in 
E. giganteum) they may be traced as externally projecting ridges over 
the nodal xylem into the internode above. In passing through the node 
they diverge from one another so that in the internode they are found 
on the adjacent sides of two different bundles. At the node above 
they approach each other, and in the next internode they both occur 
in the same bundle once again. The leaf-trace protoxylem, having 
entered the bundle, runs downwards for one internode between the two 
lateral strands ; at the node below it divides into two branches, which 
curve to the right and the left in order to fuse with the neighbouring 
leaf-traces that enter at this node. 
So the xylem of the so-called vascular bundle of Equisetum consists 
of three strands, two of which are lateral and cauline, while the 
median, or carinal, strand is common to both stem and leaf. The 
fact that only a small portion passes out as a leaf-trace, and not the 
bundle as a whole, constitutes an essential point of difference between 
it and the bundle of a Phanerogam. 
The tracheides in each strand are very few, and consequently it is 
difficult to determine the direction of their development. However, as 
regards the leaf-trace and the carinal strand, it appears clear that they 
are not exarch but endarch, or perhaps slightly mesarch on the adaxial 
side. The lateral strands, as a whole, are differentiated later than the 
carinal strand (as might be expected from the close relation of the 
latter to the leaves), but they do not seem to be a continuation of its 
centrifugal development. On the contrary, in E. giganteum , where 
is many as ten to fifteen elements are present in each lateral strand, 
he smallest of them are invariably at the outer extremity, and they 
;radually increase in size inwards. Longitudinal sections show that 
he largest tracheides are coarsely reticulate, with large pits and very 
broad bands of thickening between them ; in the smaller elements the 
eticulation becomes finer and more regular, and in the smallest it 
closely resembles true spiral thickening. To state definitely whether 
the lateral strands are exarch or not was not possible, because no 
incompletely differentiated portions of the stem were available; so the 
