16 Tansley and Lulhani. 
only put in where, at the nodes, they pass through the plane of 
the cylinder. If this figure be compared with the similar figures of 
Mettenius it will be readily seen that the outer rhizomic system is a 
much dissected dorsiventral dictyostele in which there remains one 
constant broad dorsal strand, representing a dorsal strip of the 
original solenostele, as for instance in Poly podium latipes (Mettenius 
’63, Taf. IX., Fig. 6). See Gwynne-Vaughan (’03, pp. 694—698). 
We conclude, therefore, that the vascular system of Pteris 
aquilina is a dorsiventral dictyostele of the Polypodium-type with 
an internal system of accessory strands developed in connexion with 
lateral elaboration of the leaf-trace. 
Fig. 59 , 
Fig. 59. Pteris aquilina. Diagram of the course of the vascular strands at 
a node, somewhat simplified, seen from the dorsal side. Inner strands 
of rhizome and lateral folds of leaf-trace shaded. A part of the 
dorsal outer straud is supposed to be removed, thus shewing the 
branching of the inner ones, c.s., compensation-strand. 
Fig. 59 is a diagram of the vascular system of the node of Pteris 
aquilina, drawn for comparison with Figs. 1 — 3. It is represented 
as somewhat simpler than any node we have actually seen, so as to 
avoid confusion. The inner strands of the rhizome and the petiolar 
strands in connexion with them are darkly shaded. 
