ANCIENT PLANTS 



Fig. 7. Leaf Impression of Ginkgo, of which 

 the film was strong enough to peel off complete 



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

 after treatment the cells of the epidermis were perfectly 



recognizable under the 

 with the 

 ( breathing 



microscope, 

 stomates 



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 

 vital anatomy of the 

 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 



v- 



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. 



