FERNS, FOSSILS AND FUEL 
not a cast. The organic matter has been compressed 
between the rocks in much the same manner as when we 
press a blossom between sheets of blotting paper or the 
pages of the family Bible. The external form is simply 
indicated by the stain of compressed carbon which is 
all that remains of the plant fragment. 
As a rule, we have impressions of the organs of trees 
and shrubs, but not of those of grasses and flowers. The 
leaves, seeds, and broken-off stems of trees and shrubs 
are carried into the water where they have a chance to be 
embedded in the mud and thus preserved. The grasses, 
flowers and other herbaceous plants usually decay on the 
spot and do not have organs that may easily be broken 
off and carried away. The toughest leaves and the 
woodiest fruits and seeds are the most easily preserved, 
because they can be carried some distance in the water 
without being destroyed. The soft and fragile tissues 
of grasses and flowers can be preserved only if they are 
embedded almost on the spot where they grew. 
To the paleobotanist, fossil hunting takes on all the 
aspects of a sport, although it is always a strenuous and 
sometimes a dangerous pastime. He follows up out¬ 
crops of shale in ravines, on river banks, on mountain¬ 
sides, clinging precariously while he hammers at the 
shale until the layer, sometimes only a few inches thick, 
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