102 
HISTOLOGY OF VEGETABLES. 
tissue, the latter the vascular tissue of the plant, which 
is almost entirely composed of scalariform vessels, 
arranged most frequently in a circular form. An 
FIG. 88. 
FIG. 89 . 
A bundle of scalariform vessels seen in a diagonal 
section of the root of Pteris aquilina. 
Scalariform vessel of 
hexagonal figure. 
fig. 90 . 
oblique section of the root of Pteris Aquilina , or Com- 
mon Brakes, one of the most abundant of our Ferns 
(Fig. 88), exhibits the cut extremity of a bundle of 
these vessels lying among the ligneous 
tissue ; the scalariform, or step-like 
markings of the walls, are well shown, 
and also the fact above mentioned, 
that they are not always circular in 
form, but often hexagonal or heptan- 
gular. 
In Fig. 90, which represents a por- 
tion of a vessel found in a vertical 
section of a Tree Fern of New Zea- 
land, these scalariform vessels are ex- 
One side of a 
scalariform vessel 
from a Tree Fern 
of New Zealand. 
