444 STRUCTURE AND AFFINITIES OF LEPIDOSTROBI. 



mens, is to me very satisfactory, as the Lepidodendrons, of which they 

 are the fruit, no doubt partook of this character, which is eminently 

 favourable to a rapid decomposition and intimate union with the silt or 

 mud which is the basis of the clay iron-stone in the one case, and the 

 formation of a homogeneous bed of vegetable matter, such as the coal 

 presents, in another. The extraordinary abundance of the fragments, 

 too, indicates a most vigorous vegetation, for they must indeed have 

 been profusely scattered to be deposited in such numbers within narrow 

 cylinders, into which no current appears to have been directed. 



It is worthy of remark, that no fern leaves are contained in any of 

 these Lepidodendron stems ; and their absence is the more singular, 

 from their being commonly deposited, along with branches of Calamities, 

 &c , in the erect stumps of Sigillaria resting on the coal-shales. This 

 is no doubt connected with the well-known fact of the Sigillaria stumps 

 being filled with sandstone, or the same materials as those composing 

 the stratum above the shales they root into ; whilst the fossil Lepidoden- 

 dron of the clay iron-stone seams is of the same mineral as that wherein 

 it is imbedded. Were the fragments of Lepidostrobi washed into their 

 enclosing stumps by any current, that agent would in all probability 

 have transported the remains of other plants to the same spot. 



The perfect preservation in which these fragments occur must be 

 attributed to the protection afforded them by the surrounding Lepido- 

 dendron bark. That the circumference of the latter has been subjected 

 to pressure may be inferred from the flattening of the prominences to 

 which the leaves were attached. This pressure was moreover very con- 

 siderable, as may be proved by comparing the evenness of their surface 

 with that of a piece of Lepidodendron bark fossilized without pressure 

 and embedded within the stem along with the Lepidostrobi (plate 10, 

 fig. 1). From this it may be seen that the scars of the surface occupied 

 the faces of diamond-shaped projections, elevated a full \ of an inch and 

 more above the surface of the stem, and that they were separated from 

 one another by deep grooves which dilate inwards : in other words, the 

 prominences are broader at their bases than on their surface, 



To illustrate this beautiful and hitherto unobserved character of 

 Lepidodendron bark, I have figured (plate 8, fig. 12), a unique speci- 

 men preserved in a very hard and tough iron-stone, for the loan of 

 which the Geological Survey is indebted to Mr. Cooper, of Bilston. It 

 is not known to what favourable combination of circumstances this fossil 

 owes its rare and perfect state of preservation : it is the only specimen 

 of the kind that I have seen, and, hke the Stigmaria fragments figured 

 at plate 1, it throws a new light upon the subject it illustrates. In this 

 the surface that bore each leaf projects a full i of an inch beyond 

 that of the stem itself, and is perforated by a tubular cavity through 



