Tracheids in the Node of Equisetum maximum 131 
1. Diagram of longitudinal section through node of Equisetum maximum. 
D, diaphram of thick-walled cells ; C, carinal canals above and below 
node ; T, tracheids at node, some passing out as leaf-trace. (L). 
2. Part of the same section (enclosed between the broken lines in Fig. 1) ; 
shewing a large number of reticulate tracheids at the node 
bulging out above into the canal and passing below the node into large 
broken rings of lignified tissue. Ty., tyloses from cortical cells belo.u 
node ; Px., rings of protoxylem. 
3. Tranverse section through a carinal canal just below a node of 
E. maximum, shewing a single large reticulate element nearly filling 
up the lumen. Three xylem tracheids arc seen at the edge of the 
canal. 
4. Transverse section below the node, shewing several reticulate elements 
projecting into the lumen of the carinal canal. 
5. Transverse section shewing a large meshed reticulum in the lumen 
of a carinal canal just above the node. 
Longitudinal sections were cut through the node, and, in one 
of these, two carinal canals, one above and the other below the 
node, happened to be cut (1 and 2). Into the lumina of these canals 
the large reticulate elements, which had before been seen in 
transverse section, projected, nearly filling up the ends of the 
canals. A considerable number of small reticulate elements, noted 
by Cormac, were seen to connect the larger elements. In the same 
section several tyloses were formed by the vascular parenchyma, 
and projected into the lumen of the lower canal. 1 
In order to determine whether the large reticulately pitted 
tracheids were used in conduction, a branch of Equisetum maximum 
was fastened to a vacuum pump, and one end was dipped into a 
watery solution of eosin. After two hours the solution had reached 
the top of the branch and sections were then cut in order to 
examine the regions stained. In the internodes the walls of the 
canals were very deeply stained, but towards the nodes, (i.e. as the 
reticulately pitted elements appeared and increased in number), 
their stain became very slight, while the reticulate elements all took 
the stain. The larger tracheids projecting into the top and bottom 
of the canal were also stained, but not quite so brightly as the 
smaller tracheids. 
The large xylem elements are of such remarkable character 
that it is natural to regard them as serving some special purpose. 
Their position, in the extreme ends of the canal lumina, certainly 
suggests them to be of importance in the conduction of water from 
canal to canal by means of the small reticulate tracheids. In 
longitudinal section it is seen that they are continuous with the 
small tracheids, and some of them, at any rate, must be looked 
upon as greatly enlarged extensions of these. 2 
1 Strasburgcr, loc. cit., p. 437. 
2 cf. Williamson. Phil. Trans. R. Soc., 1871. PI. 28, Fig. 40. 
