« FOSSIL FLORA. 21 



PLATE 11. 



Petrified Woods. 



Fig. 1. Silicified bituminized wood; probably from New Holland. 



Fig. 2. Silicified root of a coniferous tree, {RhizoUthes, of the early collectors,) "resembling 

 in structure that of the larch." — Mr. Parkinson. 



Fig. 3. A similar example of silicified bituminous wood, or root. 



Fig. 4. Fossil coniferous wood, a longitudinal section. 



Fig. 5. Another section of the same fossil wood. 



Fig. 6. " Petrified larch-tree," from Mount Krappe in Hungary. 



Fig. 7. Silicified bituminous wood. 



Fig. 8. " Jasperized wood, resembling in structure that of the hazel." — Mr. Parkinson. 



Fig. 9. Silicified coniferous wood ; apparently a dried and withered mass, before it underwent 

 petrifaction. 



Fig. 10. Silicified wood, having a cavity lined with mammillated chalcedony; appearing as if 

 the silex had percolated through the substance of the mass, and had slowly oozed 

 into the hollow. 



Fig. 11. Silicified bituminous wood. In this specimen the siliceous matter occurs in yellow 

 semi-pellucid globules ; the colour is supposed to have been derived from the 

 bitumen. 

 The silicified woods delineated above, belong to the division which Mr. Parkinson deno- 

 minated opaline; he conceived their peculiar characters to have resulted from an infiltration of 

 fluid silex into the ligneous tissue, which, having previously undergone bituminization, was 

 in a permeable state ; hence originated the conchoidal fracture and peculiar resinous lustre 

 which these specimens exhibit. 



The specimen, fig. 7, Mr. Parkinson describes as corroborating the opinion that the ligneous 

 tissues were converted into a bituminous substance, and subsequently impregnated with siliceous 

 matter. " In that fossil there is a knot of wood which diifers not the least in appearance from 

 that in a recent piece, but it is perfectly impregnated with opaline silex. Is it possible that 

 the change this knot has suffered could have been eifected by an abstraction of the greater part 

 or of the whole of its constituent molecules, and a substitution of particles of a different nature ? 

 Its hardness and closeness of textui-e oppose an insuperable bar to the supposition : whilst the 

 mysteriousness of the change is entirely dispelled by admitting of the softening operation of 

 bituminization, and consequent admission of silex in a fluid state." — Mr. Parkinson, 



