'4 



ANCIENT PLANTS 



In fig. 7, the impression is that of a Ginkgo leaf, and 

 after treatment the cells of the epidermis were perfectly 



recognizable under the 

 microscope, with the 

 stomates ( breathing 

 pores) also well pre- 

 served. This is shown 

 in fig. 8, where the out- 

 line of the cells was 

 drawn from the micro- 

 scope. In such speci- 

 mens, however, it is 

 only the outer skin 

 which is preserved, the 

 inner soft tissue, the 



Fig. 7.— Leaf Impression of Ginkgo, of which Vital anatOmy ot the 

 the fihn w<is strong enough to peel off complete plant, is CrUshed and 



carbonized. 

 Leaves, stems, roots, even flowers (in the more recent 

 rocks) and seeds may all be preserved as impressions; 

 and very often those from the more recently formed 



rocks are so sharply defined 

 and perfect that they seem 

 to be actual dried leaves laid ' 

 on the stone. 



Much evidence has been 



accumulated that goes to 



show that the rocks which 



contain the best impressions 



were originally deposited 



under tranquil conditions in 



water. It might have been 



in a pool or quiet lake 



with overshadowing trees, or 



a landlocked inlet of the 



sea where silt quietly accumulated, and as the plant, 



fragments fell or drifted into the spot they were 



covered by fine-grained mud without disturbance. In 



Fig. 8. — Outline of the Cells from 

 Specimen of Leaf shown in fig. 7 



c, Ordinary cells; s, stomates; v, 

 elongated cells above the vein. 



