CELLS. SILICA. 
51 
amount of silica is so great as to cause it to be employed 
in the manufacture of pottery. 
In order to display effectually the siliceous matter in 
plants, it is necessary to expose the tissue under exami- 
nation to the flame of a blowpipe, or better still to boil it 
for some days in nitric acid. By these means the 
organic portion is entirely destroyed, and the silica with- 
standing these destructive agents, remains as a perfect 
model or cast of the original tissue. 
The stem of Equisetum hyemale, after having been 
A portion of the cuticle of 
Equisetum hyemale , after long rOWS of Small OVal bodies with 
boiling in nitric acid. 
fig. 34 . 
boiled and macerated in nitric 
acid for a considerable period, 
is a mass of pure silica, and, 
as represented in Fig. 34, not 
only do the forms of the cells 
of the cuticle remain, but even a 
considerable amount of the detail 
of the stomata, as shown in the 
A portion of the cuticle of a leaf 
of the Bamboo. 
A 
fig. 35 . 
B 
serrated markings. In the leaf of 
the bamboo, Fig. 35, of which one 
part A has been imperfectly, and 
another B perfectly decarbonised, 
an exact model, or cast in silica, 
of the original specimen still re- 
mains ; the more complete the 
decarbonisation the whiter is the 
silica. On the surface of that 
part of the leaf, shown at B, even 
E 2 
