Side-Liglit upon Coal Forjnation. — Greslty. 75 
in all these cases with the fracture of the specimen, its obliquity 
and so on. Another lamina will show a somewhat open 
cellular upper and lower rind with a dense black central plate. 
Still another may consist of connected patches or expansion- 
like processes on either surface of a ? blade or ? midrib-like 
center. Then we have them apparently composed entirely 
of one kind of cell: — of rows or a cluster of seed-cases at- 
tached or detached from stalk-like connections:- — masses of 
cells gray in color, apparently perforated in a regular manner, 
by holes. And this necessarily crude list might be lengthened, 
making it evident that if future investigation shall show that 
none of the structures observed are new to coal — or to known 
coal-plant anatomy, these laminae cannot in future be said 
to be so devoid of internal organization as to prevent identifi- 
cation being some day possible. 
5. Indications of internal organization of plants in and 
composed of coaly material are, in suitable specimens and 
where favorable conditions obtain, more or less distinctly im- 
printed upon the surfaces of those scales or thin plates of 
calcareous material (selenite and gypsum) filling or partially 
filling otherwise open cracks in coal. Not only is the lamina- 
tion or grain of coal clearly portrayed upon this whitish scale, 
l)ut otherwise invisible plant-structures occupying the pitch- 
coal layers, are rendered evident. In these natural micro- 
lithographs, as I propose to call them, we find that it is the 
gray or paler colored part of the fossil which has made its 
impress in blackish "ink" upon the crystalline lime, while 
the black portion does not appear to have been affected. Here 
then we have a clear instance of the affinity of the mineralized 
hydrocarbonaceous material, occupying the cells of coal-plants, 
for the lime in the cracks in the coal-beds: the lime would 
seem to have drazvii the carbon compound out of the coal, 
because in some cases small cavities may be detected in the 
face of the coal exactly corresponding to the black markings 
or carbon prints adhering to the scales when removed. For 
the most part these lime-filled cracks are associated with the 
pitch-coal layers, and avoid the coarser, duller ones: in short, 
the more pronounced the pitch-coal laminae and the thinner 
the la\'crs of coal matrix, the stronger the scales of lime. 
-'Bird-cNc" or "lUitton-spotted" fractured coal yields tlicse tiny 
