2 1 8 LEPIDODENDREA E. 



ment of the tissue, evidently a special provision for giving firmness to the 

 plant, will be met with again more or less strongly developed in different 

 species, and especially in many Sigillariae. Cortical tissues of this kind, 

 separated from the woody bodies to which they belonged, are met with 

 not unfrequently at Autun, and received from Brongniart the provisional 

 name of Dictyoxylon, which being no longer required as a generic name 

 may now very well be used as a short expression for this peculiar structure. 

 It has been already stated in the Introductory chapter on p. 7 that we also 

 have the traces of Dictyoxylon-rinds in the form of impressions. It is 

 obvious that after the parenchyma had rotted away, impressions of the net- 

 work might in certain circumstances be formed, and in that case the 

 mineral matter making its way into the meshes of the net would form 

 irregular fusiform humps separated from one another by sharp deep furrows 

 corresponding to the ridges of sclerenchyma. It is to a state of preserva- 

 tion of this kind that Williamson 1 has referred the form belonging to 

 Sagenaria fusiformis which has been figured by Corda 2 , and also an im- 

 pression which was described by Gourlie as Lyginodendron Landsburghii, 

 and this name he has applied to a distinct collective form with a very 

 remarkable structure which he had previously named Dictyoxylon, and 

 which must be discussed further on. I have not myself seen Gourlie's 

 work ; a specimen of the state of preservation in question, which I possess 

 from the Bacmeister seam in the Hannibal mine near Essen, makes me 

 think Williamson's interpretation very plausible. 



A second very different type is presented to us in Renault's 3 Lepido- 

 dendron Jutieri. We are not in a position unfortunately to arrive at any 

 certain decision with respect to this form, since it has not up to the present 

 time been either figured or fully described. It is known only in a branch 

 one hundred and five millimetres in length and fifty-eight millimetres in 

 thickness and split longitudinally, which was found near Autun. It 

 appears from Renault's brief remarks that its thick rind consists of homo- 

 geneous parenchyma ; of its axile portion this author says : ' This specimen 

 appears to me to be without the continuous wood-cylinder which is met 

 with in our former Lepidodendrons, and which would be represented only 

 by a circle of vascular bundles giving rise to the strands which pass to the 

 leaves.' It is not even certain therefore whether we have before us a circle 

 of bundles surrounding a central pith, or a single strand with its central 

 portion formed of parenchymatous tissue and giving off a number of 

 vascular groups from its periphery. We will hope that this fossil will soon 

 be more thoroughly investigated ; its importance will appear still further 

 when we are considering the group of Sigillarieae. 



The structure of Lepidodendron vasculare, Binney (L. selaginoides, 



1 Williamson (1), iv, p. 393. 2 Corda (1), t. 4, f. 6. 3 Renault (1), p. 258. 



