100 On Different States of Fossil Vegetables. 
In this case, we can judge only of the exterior forms of the 
vegetable, and often the best means of doing it with accu- 
racy is, after carefully removing the amorphous matter which 
fills the hollow left by the vegetable, to pour into the cavity 
either wax, sulphur, or any other matter, which will represent 
exactly the forms of the destroyed vegetable. 
The impression with some preserved portions of the vege- 
table tissue is very frequent with the stems found in the’ 
coal-formation. This is their ordinary mode of preservation ; 
and here the exact determination of the different forms of 
the vegetable requires much attention. 
In the greater part of these stalks or stems, the super- 
ficial portion, a kind of thick and woody epidermis, has passed 
into the state of compact and anthraciteous coal; all the 
rest of the plant has been destroyed and replaced by clay, 
micaceous sandstone, often even by a coarse sandstone, with- 
out any appearance of organisation. Sometimes, however, 
this destruction of the internal tissues is less complete ; the 
most resistant are preserved and turned into coal ; these are 
the ligneous or vascular parts, the place of which and even 
the structure is indicated by coal lineaments. This has been 
long observed in Stigmaria ficoides, and M. Corda has often 
seen the same thing in many stems found in the coal-pits of 
Bohemia. Sometimes, besides the axis and woody cylinder 
properly so called, there is an internal cortical zone, then an 
external bark, which are likewise preserved, while the inter- 
mediate cellular tissue is destroyed. These different zones 
of denser tissue which, separated by large beds of destroyed 
cellular tissue, envelope one another like so many cylinders 
inclosed one within another, and are often preserved insulated, 
have each their special form, and often a different one on 
their external and internal surface. The same stem may 
thus produce very different forms, each cylindrical, and re- 
sembling so many different stems. 
I have long since pointed out this fact in regard to the 
stems of a Sigillaria, whose stem, deprived of its coal bark, . 
had constituted the genus Syringodendron. 
In the Lomatophloios crassicaule of M. Corda, the vascular 
axis forms a cylinder finely striated, which may be taken for 
