236 



0. II White — Autqphytography. 



by Seward,* and similar impressions in the Buntersandstein of 

 the Yosges were found by Schimper and Mougeotf to have 

 either received a deposit of hydrated ferric oxide or to have 

 had the red color of the rock removed from about the plant 

 impression, the intensification or the removal of the coloring 

 depending on the locality and the nature of the rock. In the 

 Harvard collection are representatives of both these types from 

 the Yosges and also from the Solenhofen deposits, as well as 

 from many other localities. There are also examples in which 

 the plant has left no impression or mould on the rock, but, at 

 the same time, has been perfectly fossilized by negative auto- 

 phytography. A fair representative of this class from the 

 Lias of Germany is shown in figure 5. It is a specimen of 

 Fucoides hollensis, collected at Boll, Wurtemberg. 



The various classes of evidence for the existence of plant 

 life may be summarized as follows : 



f Direct < 



Evidences \ 



of plant life < 



Yegetable substance 



Mould or impression 



Cast 



^ Autophytograph 



Original tissue 

 Carbonized 



External form only 

 Internal structure 

 Positive 

 Negative 



Indirect .. Graphite, coal, sinter, bog-iron-ore 



Harvard University, Cambridge, Mass. 



* A. C. Seward, Fossil Plants, vol. i, p. 68. 



f Schimper et Mougeot, Monographie des plantes f ossiles du gres bigarre 

 de la Chaine des Vosges, p. 10. 



