DESCRIPTIVE LIST 
OF THE 
Principal Groups of Fossils in the Collection, 
AND WHERE TO FIND THEM IN THE CASES. 
PLANT REMAINS. 
Plants are usually found fossil in detached fragments, and are 
generally known only by the remains of individual leaves or 
fragments of wood. Especially is this the case with our common 
forest vegetation, as the leaves are blown into streams and carried 
to the ocean, or into lakes, where they become buried in the 
sediment and preserved. Fragments of trunks or limbs of trees 
are preserved in the same manner. Petrified forests are only 
formed where a wooded region is suddenly submerged by waters 
heavily charged with mineral matter, caused by some volcanic 
action. Two beautiful sections of mineralized wood of this nature 
are placed upon the mineral case No. 5. The vegetation of the 
Coal period is often found in a very perfect condition of preser- 
vation, owing to the peculiar conditions under which it lived and 
became imbedded ; nearly entire trunks are often found, and 
many times in an erect position. The accompanying cut of an 
ideal coal forest (taken from Dana's Manual of Geology) will give 
a good idea of these conditions, and the restored figures (after 
Dawson) show the form of the trees of the period to which they 
belong. 
