8 
HISTOLOGY OF VEGETABLES. 
cannot be demonstrated until charred, or stained of a 
brown colour by the application of tincture of iodine. 
Examples are not unfrequently met with in which 
cells or vessels having become old and dry, the mem- 
brane has disappeared, and holes have been left, and 
such is the case in the vessel from a Balsam , Fig. 2, a. 
FIG. 2 . 
A B 
a, old cell from the Balsam exhibiting perforations, b, fibrous cells of 
Sphagnum with perforations. 
True foramina, however, are found in the walls of 
newly developed cells in certain mosses of the genus 
Sphagnum. These cells (Fig. 2, b), are of a fusiform 
shape, have a spiral fibre developed within them, and ex- 
hibit a series of perforations on each side, which were 
first described by Mr. W. Valentine. I have satisfied 
