90 
HISTOLOGY OF VEGETABLES. 
pores, a tangental section of the wood must be made ; 
when, as in the specimen of deal (portions of two con- 
tiguous fibres of which are represented by h c , in Fig. 
77,) it will be seen that there are certain oval spaces 
between these fibres, which have in their centre a pore 
extending nearly through the entire thickness of the wall 
of the fibre, but closed by membrane on its outer margin ; 
a highly magnified representation of one of these pores, 
showing the mode in which it projects from the side of 
the woody fibre of the deal, is shown at d. The correct- 
ness of this account of the real significance of the struc- 
ture of the glandular woody fibre has been strikingly 
confirmed by the examination of sections of fossil coni- 
ferous wood. Some years since, a specimen of fossil wood 
from Fredericksburgh, in Virginia, was sent to my late 
brother by Professor Bailey of the Military Academy of 
West Point on the Hudson, which, on microscopic ex- 
amination, was found to be coniferous, the woody tissue 
not only exhibiting the bordered pores, but, in addition, 
numerous minute spiral fibres, as represented in Fig. 7 8, 
A. Some of the disc-like bodies, shown at a a in the 
same figure, and precisely similar to the pores of the 
fibres, were lying loose. On carefully examining the 
surfaces of the fibres, similar discs were occasionally 
found projecting from the outer surface, as represented 
in Fig. 78, a. It then turned out that these dies were 
in reality casts in silica of the bordered pores ; in short, 
the bi-concave cavities shown by b c in Fig, 77, had 
been filled with silica. Thus the description given of 
