Stem of Angiopteris evectct. 
505 
Vascular System in the Stem. 
In the determination of the course of the vascular strands 
in the stem of A. evecta , two methods of working were found 
most successful. 
The comparison of successive transverse sections in the 
first place gave information as to the origin of the leaf-trace 
bundles, the method of compensation from zone to zone, and 
the origin and passage to the exterior of the roots. 
A clear conception of the arrangement of the vascular 
tissues into a network could, however, only be gained by the 
removal of the parenchymatous tissue and the exposure of 
the strands. 
Softening the tissues by boiling in potash was found in¬ 
expedient, as, though the labour of removing the parenchyma 
was thereby much diminished, the vascular strands became 
too weak to maintain their relative position. It was found 
most satisfactory to pick away the parenchyma with a sharp 
knife, and thus expose the vascular tissue. 
In accordance with the dorsiventral structure of the stem 
as seen from the exterior, the vascular network was found to 
be different in character on the two sides of the stem. This 
is seen at once by comparing Figs. 5 and 6, which represent 
the superficial vascular tissue on the upper and under side of 
the stem respectively. In Fig. 5 strands from more deeply 
lying vascular zones are also represented. 
On the upper surface of the stem the meshes of the network 
are small and more or less square in outline; the strands 
destined for the leaves form obliquely ascending portions of 
the vascular framework, which stand one above another at 
short intervals. If the dissected stem, shown in surface-view 
in Fig. 5, is seen from the side, the strands bending out 
into the leaves appear as projecting and curved bracket-like 
portions of the stelar lattice-work. 
In Figs. 5 and 6 the strands belonging to the same leaf 
have the same lettering; thus in Fig. 5, the bundles marked 
