BIBLIOGRAPHY. 



107 



show how much this included cylinder has embarrassed those who have considered it with 

 a view to the vegetable organ to which it owes its origin. In the specimens of Calliard, 

 which have suffered little compression, but which are seldom above a few inches in length, 

 this body is generally nearly central ; perhaps in no instance perfectly lateral. In the 

 specimens in clay, from one of which we were able to detach upwards of 6 feet, the 

 flattened or grooved side is invariably downward ; and consequently the included cylinder 

 is in the position which it would assume if it had subsided at one end, while the other was 

 supported, or which would be the result of its sinking through a medium of nearly the 

 same specific gravity with itself, provided it was at one end rather denser than at the 

 other. It must be observed that this included body appears to have suffered various 

 degrees of compression, being sometimes cylindrical, which was evidently its original 

 form, and sometimes almost entirely flattened. In the coal shale we were never able to 

 detect a trace of its existence. 



" Besides these indications of organisation, we have met with several specimens which, 

 on being longitudinahy split, discovered marks of perforations or fibres, more or less 

 parallel with the axis of the cylinder, and in some degree resembling the perfora- 

 tions of Terebellse in the fossil wood of Highgate and some other places. Whether 

 these configurations be owing to the organisation of the original vegetable, or to some 

 process which it underwent during its decay, seems impossible to determine ; the 

 specimens examined afforded no opportunity of discovering a connection between these 

 tubes and either the internal cylinders or the external surface. 



" Among the vast number of specimens examined, only one was detected which 

 appeared to terminate, closing from a thickness of 3 inches to an obtuse point. We 

 have given a figure of it, pi. 4, fig. 3. Two instances also came to our knowledge of 

 branched specimens, in which the trunk divided into nearly two equal branches. So rare 

 an occurence of this circumstance would, however, rather induce the supposition that the 

 original was properly simple, and that these were only exceptions or monstrosities. The 

 size of different species varies greatly; but we have seen none under 2 inches in 

 diameter ; the general size is 3 or 4, and some occur, but with very indistinct traces 

 of the pustules, even 12 inches across. 



" From the above, it appears rational to suppose that the original was a cylin- 

 drical trunk or root, growing in a direction nearly horizontal in the soft mud at the 

 bottom of fresh-water lakes or seas, without branches, but sending out fibres from all 

 sides ; that it was furnished in the centre with a pith, of a structure different from the 

 surrounding wood or cellular substance, more dense and distinct at the older end of the 

 plant and more similar to the external substance towards the termination, which 

 continued to shoot ; and perhaps that, besides this central pith, were longitudinal fibres 

 proceeding through the plant, like those of the roots of the Pteris aquilina. With respect 

 to any stem arising from it, if a root or foliage belonging to it, if a creeping trunk, we 

 have hardly ground for a supposition." 



