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agent. More frequently the preservation is due to 

 incrustation ; as resin trickled down the stems of the 

 Tertiary pines from an open wound, flowers and 

 leaves, blown by the wind on to the sticky surface, 

 were eventually sealed up in a translucent case of 

 amber. Though the actual substance may have gone, 

 the mould which remains exhibits in wonderful per- 

 fection each separate organ of a flower or the 

 delicate hair-clusters on the surface of a leaf. The 

 flower represented in Fig. 8, a species of Cinnamon, 

 is one of several specimens described by tlie authors 

 of a monograph of Tertiary plants in the Baltic 

 amber{4i). 



The fragments of plants preserved in nodules of 

 calcareous rock occasionally met with in some of the 

 Lancashire and Yorkshire coal-scams are perhaps 

 the most striking examples of the possibilities of 

 petrifaction. By cutting sections of these nodules 

 and grinding them to a transparent thinness, the 

 most delicate tissues of Carboniferous plants are 

 rendered accessible to investigation under the high 

 power of a microscope. As our attention is absorbed 

 by the examination of the details of cell-structure 

 it is easy to forget that the section has not been 

 cut from a living plant, but from the twig of a 

 tree which grew in the forests of the Coal age. The 

 preservation is such as to enable us not only to 

 describe the anatomy of these extinct types of 



