THE NATURE OF SOME SUPPOSED ALGAL COALS.i 



By Edward C. Jeffrey. 



Presented April 14, 1909. Received Aug. 12, 1910. 



Early in the last decade of the nineteenth century MM. Renault 

 and Bertrand published simultaneously their views as to the constitu- 

 tion of so-called boghead and similar coals.^ In the bituminous schists 

 of Autun are apparent even to the naked eye glistening spherical or 

 oval bodies often arranged in layers, which readily reveal themselves 

 under the microscope, in thin sections made in the manner of the rock 

 sections of the petrographer and mineralogist. These objects are of 

 considerable size, their dimensions ranging between 189 and 225 micra 

 in length and between 95 and 115 micra in breadth. They have been 

 named on account of their shape and locality Pila bibractensis. The 

 individuals of this species when examined microscopically sometimes 

 show more or less clearly a central cavity, which is surrounded by a 

 wall sculptured with numerous alveoli, opening to the outside but 

 having no communication with the internal space. The two authors 

 cited agreed in regarding these structures as representing the remains 

 of colonial gelatinous green Algae. The central cavity, which always 

 appears in the better preserved specimens, was regarded as the equiv- 

 alent of the hollow space in the midst of a colony of the living Volvox, 

 or an allied genus of the colonial Algae. The substance surrounding 

 the cavity, according to the hypothesis of the French authors, repre- 

 sents the gelatinous wall of a former algal colony, while the external 

 openings or alveoli are imagined to correspond in their position and 

 relations to the once living individuals of the colony. The hypothesis 

 of the algal nature of the organism found in such abundance in the 

 bituminous schists of Autun, was later extended by its authors to a 

 wide range of similar organisms occurring in bogheads and cannels, 

 as well as bituminous schists and oil-shales from various parts of the 

 world. Their most notable subsequent communications on this sub- 



^ Contributions from the Phanerogamic Laboratories of Harvard Univer- 

 sity, No. 23. 



^ Renault, B., Communication faite sur le Boghead, Soc. Hist. Nat. Autun, 

 1892; Bertrand, C. E., Pila bibractensis et le Boghead d' Autun, Soc. Hist. Nat. 

 Autun, 1892. 



VOL. XLVI. — 18 



