362 Mr W. NicoPs Observations on ike Fossil Trees of 



ture is quite obliterated, and the ligneous origin can barely be 

 inferred from very slight traces of annual rings. Some parts 

 have a fibrous structure^ and are white and opaque. The fibres 

 cohere so slightly in some portions, that they may be reduced to 

 powder between the finger and thumb. In general, however^ 

 the fibres cohere more firmly as they approach the translucent 

 part, and then the vegetable structure becomes very apparent. 



In addition to the above specimens, I have in my possession 

 other two from Van Dieman's Land. These are both Coniferae, 

 so that out of nine specimens seven are Conifers?, and only two 

 true Dicot37ledons. As far as these nine specimens go, we may 

 therefore infer, that in Van Dieman's Land the growth of coni- 

 ferous trees at a period antecedent to the present state of things, 

 was more frequent than that of the Dicotyledonous kinds. The 

 same may be said with regard to the Coal and Lias formations 

 of this island. In these deposits numerous specimens of petri- 

 fied wood have been found, and, from a careful examination of 

 these, I will venture to assert that the whole belong to the coni- 

 ferous tribe. This opinion you will probably remember I men- 

 tioned to you, Mr Witham, and others, in the course of last 

 summer, and I was then led to speak on the subject with some 

 degree of confidence, from a recent investigation of the structure 

 of the different kinds of trees at present growing in all the diffe- 

 rent climates of the globe. In order to obtain the requisite know- 

 ledge, I found it necessary to cut transverse sections of a great 

 number of trees, and of such a degree of thinness, that the cel- 

 lular, as well as the vascular, system might be distinctly seen. 

 This labour I was obliged to submit to, in consequence of find- 

 ing all the sections of wood figured in such works on vegetable 

 anatomy as I could lay my hands on so imperfect, that no pre- 

 cise idea could be formed on the subject. 



The structure of the Coniferae differs so widely from that c^ii 

 the true Dicotyledons, that a single glance will in general ena^a 

 ble us to distinguish the one tribe from the other. In the Conifer ' 

 rae there is only one regular system of pores, resembling a piece of 

 the most delicate network. Each mesh is bounded by straight'! 

 Jines crossing each other at nearly right angles, and the concen-^ 

 trie hues of the meshes almost always approximate each other at 

 the outer edge of each annual layer of the wood. This struc- 



