282 PROCEEDINGS OF THE AMERICAN ACADEMY. 



seen in several other instances in the section, while in the case of most 

 of the organisms, the structure has suffered a good deal from the 

 ravages of pressure and chemical metamorphosis. Figure 19, Plate 4, 

 shows another section in the vertical plane of the same coal presenting 

 somewhat similar appearances. This preparation, however, shows some 

 of the bodies composing the coal in a darkened and chemically much 

 modified condition, especially in the upper part of the field. Figure 

 20, Plate 4, represents a section through this boghead parallel to the 

 planes of layering. Obviously some of the parts are better preserved 

 than are others. In the well-preserved regions, which are distinguish- 

 able in figure by their lighter color, there is the same mottled appear- 

 ance, which is characteristic of tangential sections of the spores known 

 in the investigations of Renault as P'da kentuchjana and P. scotica. In 

 the darker parts of the figure, the characteristic organisms of the coal 

 have largely lost their structure and the accompanying swelling has 

 almost completely obliterated the surface sculpture. Figure 21 illus- 

 trates another horizontal section of the coal under discussion, some- 

 what more highly magnified. On the upper left hand can be seen 

 one of the constituting organisms of the coal in plane of section show- 

 ing at once the profile and the face view of its wall. The profile view 

 is the one sharply focussed and it presents all the appearance of a 

 section through the wall of a macrospore of one of the existing Lyco- 

 podiales. In view of what has been learned regarding the structure 

 of the American and Scotch species of Pila in the foregoing paragraphs, 

 it can scarcely be doubted that the micro-organisms of the coal at 

 present under discussion are also of the nature of spores of vascular 

 cryptogams. The general arguments against the algal nature of these 

 and similar bodies may, however, profitably be deferred to the end of 

 the article. 



Figure 22, Plate 4, shows a section parallel to the planes of stratifi- 

 cation of the classic Scotch boghead, known as Torbanite. I owe this 

 material as well as that of the other Scotch coals examined to the 

 kindness of Captain Halberstadt. In this case the micro-organisms 

 are in the condition of disorganization, which is generally found in the 

 French bituminous schists to be discussed below. Certain faint lines 

 are the only indication of structure presented by the light-colored 

 bodies appearing in the microscopic field represented by the figure. 



The Boghead of Autun. 



Figure 23, Plate 4, shows the horizontal view of one of the micro- 

 organisms of the boghead of Autun, first studied by Renault and 

 Bertrand. The structure is almost obliterated by swelling and chemi- 



