LIGNITES. MOLASSE. 



S7 



bustible in the neighbourhood of Cologne. All these lignites 

 appear to have been formed chiefly from con'ifers, the structure of 

 which (fig. 166) maybe recognised in the mass of combust ble 

 itself, or in the wood disseminated through various deposits. 

 C. 



B. b. c. 



fig, 166. Structure of the wood of con'ifers. 

 a. Part of a transverse section of natural size. 

 6. Part of the same section seen under a microscope. 



c. Longitudinal section, in the direction from B to C, also magnified. 



d. Section in the direction from A to B. 



23. But the tertiary sandstones of the miocene period (the mo- 

 lasse) also contain a great quantity of dicotyledonous plants, the 

 wood of which is here and there found disseminated, sometimes in 

 a silicious state, and clearly exhibiting the proper tissue or struc- 

 ture of this class of plants (fig. 167), particularly characterized 

 by the presence of large longitudinal vessels. We also find leave? 

 C. 



a. B. 6. 



Pip. 167. Structure of the wood of dicotyledons. 



a. Part of a transverse section of natural size. 



b. Part of the same section, seen under the microscope, showing the large 

 vessels. 



c. Longitudinal section in the direction from A to B, showing the struc 

 ture of the medullary rays, and that of a large vessel. 



22. What is lignite ? From what family of plants were these lignites 

 probably formed 1 How is this family of plants recognised 1 



23. What description of plants exist in the terti.iry sandstone a? the 

 miocore period 1 



