26 INTRODUCTION. 



But there are cases of the kind which we are describing, in which the 

 membranes are preserved and converted into thin black laminae of coal, 

 and appear on a transverse section of the clay casts as delicate black lines 

 like strokes of a sharp lead pencil. Such cases occur, for example, in 

 fragments of plants preserved in the Coal-measures of Niedzielisko near 

 Jaworzno in the district of Cracow, for a knowledge of which I am indebted 

 to the kindness of their discoverer, F. Romer ; his more exact account of 

 them will be found in another place. The specimens collected in the year 

 1865 are irregular obscurely stratified fragments of a very fine clay which 

 may be cut with a knife, of a grayish white colour, but here and there 

 rendered quite black by the amount of coal contained in it ; each fragment 

 has layers and glands of crystalline pyrites occurring in its substance and 

 a rind of impure coal. These fossils come possibly from local lenticular 

 deposits of clay in the seams, such as are found, according to Stur 1 , in all 

 the fissures of the coal-seams of Rakonitz in Bohemia, but more exact 

 investigation on the spot is no longer possible, as the works have been 

 abandoned. They contain seeds of Gymnosperms which are simply in- 

 crusted and have their testa converted into glistening coal, and with 

 them numerous objects in the state of preservation of which we are 

 speaking. Among these, pending more thorough investigation, may be 

 mentioned small well-preserved stems of Sphenophyllum, leaf-stalks of 

 Ferns, leaves of Lepidodendron, and a remarkable inflorescence of Cala- 

 maria. The remains showing structure from quarries of the sandstones 

 of the Coal-measures at Chomla near Radnitz, described by Sternberg 2 

 and Corda 3 , belong to the fossils which occupy an intermediate position 

 between incrustation and true petrifaction. In specimens of Cycadites 

 involutus, Sternb., which I have had the opportunity of examining, the 

 enveloping or petrifying agent is a hard and very fine-grained clay. 



Further, Goppert 4 found pure copper filling the lumina of single 

 cells and of the large vessels in a piece of recent beech-wood from Mol- 

 dowa in the Banat. The copper appeared everywhere on the transverse 

 section in the form of scattered roundish glistening points. On the other 

 hand it is extremely doubtful whether the branches of Ullmannia in 

 argentiferous copper-glance from Frankenberg in Hesse is of the class of 

 fossils which we are considering ; these fossils, where they are really petri- 

 fied, are converted into calc-spar ; the sulphur seems to have produced 

 rather incrustation and the filling of fissures ; we do indeed here and there 

 find casts of cells in this substance, so that a similar process to the filling 

 of the cells with argillaceous earth mentioned above may have taken place 

 also here. The pure sulphur may like the pyrites originate in the reduction 



1 Star (2), p. 647. * Sternberg, Graf von (1). * Corda (1). 4 Goppert (17), p. 73<5. 



