364 EKNEST WARREN. 



normal tliickness and are of a yellow colour. The section 

 is viewed with crossed prisms. On the right of the section 

 the tissue is obliterated and a radiating spherulitic structure 

 is observable. 



The calcium carbonate can apparently pass with difficulty 

 into the substance of the walls of the woody tissue, but with 

 much less thoroughness than with silica. It appears to par- 

 tially impregnate and embed the organic structure, rather 

 than to actually replace it as in the case of silica. According 

 to the tangential section in PI. XXV, fig. 9, a partial decom- 

 position of the wall of the tracheides {rj.t.ic.) was taking 

 place at the time of the penetration of the mineral substance. 

 The outer swollen portion is diffusely yellowish, due probably 

 to the impregnation of the mineral substance with decompos- 

 ing organic matter, while the central layer of a deeper colour 

 would appear to represent the less decomposed portion of the 

 wall. In fig. 8 is seen the shadowy, decomposed walls of 

 tracheides, but on the right-hand side a few less swollen walls 

 are observable. 



The whole fossil is very solid, and there are practically no 

 spaces left. A newly chipped off piece was carefully weighed 

 and then immersed in water for a short time. On removal, 

 and after being wiped, there was no difference in the weight, 

 thus showing that the Avater Avas unable to enter the fossil. 

 In the case of the phosphatized specimens and with some of 

 the silicified woods, a very marked diiference in weight was 

 at once observable (see table, p. 358). 



DICOTYLEDONOUS WOOD. 



(1) MODE OF OCCURRENCE AND GEOLOGICAL HORIZON. 



Specimens of a black, somewhat friable, fossilized wood 

 have l)een received from various sources from different pai-ts 

 of the coast of Zululand. Subsecjuently some specimens 

 collected bv the Natal Geological Survey were obtained. 



