10 
HISTOLOGY OF VEGETABLES. 
Vine , as at Fig. 3, d ; or it may be seen to still greater 
advantage in the elongated cells known as porous or 
FIG. 3 . 
A BCD 
a, pitted or dotted tissue of the pith of the Elder, b c, pitted ducts from the 
root of Marchantia polymorpha. d, pitted cells of the Vine ( Vitis vinifera). 
dotted ducts, specimens of which are readily obtained 
from the Alder. 
In all these examples there are no apertures in the 
membrane or cell-wall ; but in some old cells from 
the stem of a Balsam , Fig. 2, A, the membrane has 
been destroyed, and holes are left. This destruc- 
tion of the cell-membrane is particularly evident, both 
in the cells and vessels of many specimens of fossil 
wood, which no doubt had undergone some slight 
