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The leaves of trees are only found in substances which 

 appear to be of modern formation. Among these are said 

 to have been found those of the willow, the pear-tree, mul- 

 berry-tree, and of several others. These have been found 

 in fossil calcareous stone, chiefly in that of Oeningen, and 

 in the calcareous tufa bordering those lakes and rivers 

 which abound in calcareous matter. Leaves are sometimes 

 found in the old red sandstone, somewhat resembling those 

 of trees, but which most probably have belonged to aquatic 

 plants. 



In the grey chalk, small white ramose forms are found, 

 which pervade the chalk, and have the appearance of being 

 of vegetable origin. My attention was first drawn to these 

 remains by Mr. Mantell, of Lewes, who has illustrated 

 this subject in his excellent work on the Fossils of the 

 South Downs. 



Wood, and other vegetable substances, are frequently 

 found in clay and limestone, in the state of charcoal. It 

 cannot always be ascertained by what means this change 

 has been effected ; but in that which is found in the blue 

 clay, and in other situations in which pyrites prevail, the 

 change may safely be attributed to the decomposition of the 

 pyrites with which those substances had been impregnated. 



Mosses, Confervce, fyc. Rounded pebbles, called moss 

 agates, are frequently found on the coast of the North 

 Riding of Yorkshire : and Dr. Macculloch describes them 

 as having been found on the shore at Dunglas, in Scot- 

 land, containing substances which have the appearance of 

 vegetables. 



Daubenton and Blumenbach had expressed their con- 

 viction of the vegetable origin of these substances; still 

 many considered them as entirely mineral : but Dr. Mac- 

 culloch, pursuing this inquiry with his usual zeal and acute- 

 ness, observes, that deception is very likely to arise in 

 these specimens, from the well known metallic arborizations 



