FILICES. 157 



Scarborough ; when it was first found it was taken for an alga and named 

 Tympanophora 1 ; it was subsequently recognised by Williamson 2 as the fructi- 

 fication of a fern, Pecopteris Murrayana. This view has since been worked 

 out by Bunbury 3 and Leckenby 4 and illustrated by figures. Saporta 5 has 

 retained the name Coniopteris given by Brongniart for this fructification in 

 spite of its great resemblance to our living Thyrsopteris ; and this course is 

 in my opinion worthy of imitation, because it shows caution. If Thyrso- 

 pteris schistorum 6 from the roofing-slates of the Culm of Moravia and 

 Silesia really belongs to this genus, which from the habit does certainly 

 appear to be the case, this would be a very ancient type ; but on this point 

 Stur himself speaks with all reserve. 



Several fern-leaves from the Jurassic system are placed by Heer 7 in 

 the genera Dicksonia and Asplenium solely on account of the habit of the 

 sori as preserved in impressions ; thus we have Dicksonia Saportana, Heer 

 (Scleropteris, Sap.), and Asplenium spectabile, Heer, and A. Whitbyense 

 (Cladophlebis, Auct.). It is no longer necessary to insist at length on the 

 precariousness of this determination. Lastly must be mentioned the genus 

 Stachypteris, Pomel, from the Coralline Oolite of Verdun, in which bipinnate 

 leaves resembling those of Cheilanthes show segments of the third order of 

 abnormal and peculiar form, the supposed fertile pinnules. Its discoverer 

 Pomel compared it with Lygodium ; Saporta 8 does not assent to this, and 

 would refer it rather to Onychium. 



INNER LEAF-STRUCTURE, RHACHIOPTERIDAE AND FERN-STEMS. In 

 connection with the above account of the leaves of fossil Ferns anoT of the 

 fructifications which they bear we may now proceed to consider certain 

 anatomical peculiarities such as are described in the works of William- 

 son 9 and Renault 10 , and which are disclosed by sections of the laminae 

 of petrified leaves. In general it appears that the structure of fern- 

 leaves in the period of the Coal-measures was essentially the same as 

 that of recent species, being as a rule distinctly bifacial with several layers 

 of palisade-cells on the upper and spongy parenchyma on the under side. 

 The nerves also, which often project strongly on the back of the leaf, are 

 formed in the normal manner either of one strand of vascular bundles, or of 

 several variously fashioned and concentric strands. Tissues also with 

 mechanical function are often present in the form of strips of sclerenchyma 

 beneath the epidermis of the upper side of the leaf, often with local 

 strengthening ribs like bands, as in Pecopteris Geriensis n . In other cases, 

 as in the Alethopteris figured by Renault 12 , the subepidermal strips of 



1 Lindley and Hutton(l), vol. iii, 1.170. 2 Brongniart (2). 3 Bunbury (1). 4 Leckenby (1). 

 5 de Saporta (4). 6 Stur (6) and (4). 7 Heer (5), vol. 4 II, t. 2, ff. 16-18 and 21. * de 



Saporta (4), vol. i, p. 379; t. 49. Williamson (1), vi, vm. 10 Renault (2). n Renault 

 (2 % vol. Hi, t. 22. ia Renault (2), vol. iii, t. 27. 



