352 PEOCEEDINGS OP THE GEOLOGICAL SOCIETY. [April 24, 



The large series of specimens belonging to Mr. Daintree, as weU 

 as those already in the Museum of the Geological Society, are all 

 merely casts, generally in a finely grained rock, which must have 

 been deposited as a very fine mud, as it has insinuated itself between 

 the leaves, filling up every crevice, and preserving the parts, allowing 

 for the compression they have received in the compacting of the 

 beds, in their natural relations, Sometimes the interior of the stem 

 is filled with the amorphous material of the rock, and exhibits on 

 both its surfaces the leaf-scars as in fig. 9 of Plate XXVI. and in 

 several large trunks. 



Lepidodendron nothum, Ung., had for its roots a Stigmaria 

 which cannot be separated from S.Jicoides. The actual connexion 

 of the stem with the roots is not shown in any of the specimens ; but 

 that this is their relation cannot be doubted, as these are almost the 

 only fossils found in the beds, and certainly the only ones that could 

 be thus related. 



The leaf-scars vary considerably in size in different parts of the 

 stem, and Avhen not affected by pressure are rhombic in form. The 

 largest scars are shown in fig. 12 (PI. XXVI.) ; and these are without 

 any scar from the vascular bundle. This scar is generally present, but 

 it does not always occupy the same position in the larger leaf-scar ; 

 sometimes it is in the centre, as in fig. 10 ; sometimes at the apex, 

 as in figs. 8 and 11 ; and in others it gives a longitudinal impres- 

 sion extending from nearly the bottom to the top of the scar (fig. 9). 

 This is as might have been expected, seeing that the small scar is 

 produced by a portion of the tissue which was more persistent than 

 the parenchyma that surrounded it, and which was able to offer 

 some resistance to the soft mud that filled the decayed cavity of the 

 stem. The direction of this vascular bundle was upwards and out- 

 wards from the vascular cylinders, as in other Lepidodendrons, and 

 as is shown in Unger's specimens. Freed from the surrounding 

 cellular tissue, but yet attached to the vascular cylinder at the one 

 end and to the indurated cicatrix at the other, it might retain its 

 position in the centre of the scar, or be carried to one or the other 

 end of it by the pressure of the invading mud, according to the direc- 

 tion in which the mud came, or might even be pressed against the 

 cicatrix throughout a considerable portion of its length. It is thus 

 obvious that the position of the scar and the presence of a furrow 

 introduced by Dr. Dawson into his diagnosis of the genus and species 

 are of no value. 



The form of the leaf-scar is also liable to considerable variation 

 from pressure. Two such forms are given in figs. 13 and 14. 



The increase in the size of the scars in proportion to the dimen- 

 sions of the stems on which they are borne, may be traced in the 

 figures 7, 8, 9, 10,11 and 12. In the first three of these figures the scars 

 are suddenly fiattened, and pass into subtriangular and ultimately 

 into narrow linear scars. This condition Dr. Dawson considers due 

 to the large Ster7ibergia-])ith. showing through the thin bark ; but 

 it is really owing to the incomplete development of the bases of the 

 leaves. There has been an interruption to the growth where the 



