180 



THALLOPHYTA. 



[CH. 



The nature and manner of formation of the various forms of 

 coal should be dealt with in a later chapter devoted to the 

 subject of plants as rock-builders, but in view of the recent 

 statements as to the algal nature of these bituminous deposits 

 it may not be out of place to state briefly the main conclusions 

 of the French authors. 



MM. Renault and Bertrand regard each of the yellow bodies 

 in the European and Australian Boghead as the thallus of an 

 alga. To the form which is most abundant in the Kerosene 

 shale they have given the generic name of Reinschia, while 

 that in the Scotch and French Boghead is named Pila. 



Reinschia. Fig. 36, 3. 



A section of a piece of Kerosene shale at right angles to 

 the bedding appears to be made up of fairly regular layers of 

 flattened elliptical sacs of an orange or yellow colour. Each sac 

 or thallus is about 300/1- in length and loO/i, broad (fig. 36, 3). 

 A single row of cells constitutes the wall surrounding the 

 central globular cavity. The cells are more or less pyriform in 

 shape, and the cell-cavities are filled with a dark substance, 

 described by Renault and Bertrand as protoplasm, and the cell- 



FiG. 36, 1. Section of a piece of Scotch Torbanite. Slightly enlarged. 



2. Pila bibractensis from the Autun Boghead, x 282 (after Bertrand). 



3. Reinschia Australis, from the Kerosene shale of New South Wales, x 592 

 (after Bertrand). 



