SPECIMENS OF FOSSIL WOODS IN NATAL MUSEUM. 37 



EXPLANATION OF PLATES XXV AND XXVII, 



Illustratinc^ Dr. Ernest AVarren's paper " On Some Specimens 

 of Fossil Woods in the Natal Museum." 



Fig. 1. — X 500. Mus. No. 174. Harrismith. Small piece of trans- 

 verse section of Dadoxylon completely silicified. The walls of the 

 traeheides are of silica with practically no lignin remaining;. The 

 cavities are filled with silica. The silica may he hlackened by dark 

 granules of iron oxide or jjossiljly fixed carbon. 



Fig. 2. — x 500. Mus. No. 174. Harrismith. Transverse section of 

 Dadoxylon wood. It passes through a compression band or sheering 

 ai-ea occurring in the spring- wood. It should lie noticed that the bent 

 medullary rays in the band are not much flattened, and there is no 

 distortion as in the traeheides. 



Fig. 3. — x 750. Mus. No. 220. Weenen. Small piece of transverse 

 section of phosphatized Dadoxylon wood. The calcium phosphate 

 forms casts of the tracheide cavities. The actual wall of the tracheide 

 has mostly disappeared except at o.t.iv. This may be either the remains 

 of the original lignin wall or a silicified representation of it. 



Fig. 4. — x 750. Mus. No. 220. Weenen. The same as fig. 3 

 viewed with crossed prisms. It should be noticed that a dark 

 reticulum is visilile. this l^eing due to the fact that the outer portions 

 of the casts have a different optical reaction to the inner portions. 



Fig. 5. — x 250. Mus. No. 220. Weenen. Transverse section of 

 phosphatized wood. A compression Ijand is seen in the spring-wood. 

 This was prodiiced subsequently to fossilization since the calcified 

 structure is observed to be shattered. 



Fig. 6. — x 500. Mus. No. 220. Weenen. Transverse section of 

 phosphatized wood througli a compression band. The cells of the band 

 were clearly squeezed out of shape before complete fossilization. The 

 medullary rays in the band are not greatly aifected. 



Fig. 7. — X 200. Mus. No. 12. Ingwavuma. Transverse section 

 of calcified Dadoxylon wood viewed with crossed prisms. The 

 fossilizing sub.stance is calcimn carbonate. The structure of the wood 

 is poorly preserved, probably through the lack of the power on the 

 part of the mineral substance of easily replacing the lignified material 

 of the tracheide walls. 



Fig. 8. — x 400. Mus. No. 12. Small piece of transverse section 

 showing moderately well-preserved ti-acheide walls on the right, but on 

 the left only shadowy swollen walls are observable. 



