70 PBOIOPTEKIS. 



the form of the leaf-trace being the chief characteristic on which 

 the species -was founded. 



In the British Museum Collection there are three specimens 

 which I have referred to Schenk's species ; two of these are simply 

 casts without any minute structure, but the other is in a much 

 better state of preservation and enables us to amplify the original 

 diagnosis of the species. 



Stem with a central axis consisting of band-form vascular 

 bundles enclosing a fairly large pith; from these vascular plates 

 branches pass out to the petioles, and in a surface-view of a leaf- 

 stalk base the leaf-trace is shown to present more or less clearly 

 the characteristic horse-shoe pattern. 



The oval petiole scars are arranged fairly closely ; towards the 

 periphery of each is a single vascular bundle of the horse-shoe 

 form, but differing from that of P. punctata in the absence of the 

 distinct constriction which occurs in each limb of the leaf -trace ; 

 the free upper ends of the leaf-trace are distinctly curved inwards. 

 Sections of adventitious roots occur in the lower part of the petiole 

 scars. Between the leaf-bases there is a mass of filamentous tissue, 

 traversed here and there by irregularly disposed roots. 



Before describing in detail the specimens of Protopteris Witteana 

 in the National Collection, it should be pointed out that they 

 appear to differ in no very important characters from the widely- 

 spread P. punctata. Possibly the Wealden specimens at present 

 referred to the species instituted by Schenk, may eventually find 

 their proper place under P. punctata ; but at present we may 

 regard the slight difference in the pattern of the leaf-trace bundles 

 of the two forms as sufficient reason for the retention of Schenk's 

 Wealden species. 



In Protopteris punctata, Stemb., we have one of the best known 

 fossil tree-ferns. The species was first instituted by Presl for a 

 plant previously figured and described by Sternberg as Lepido- 

 dendron punctatum} Sternberg's specimen was for some time 

 referred to as having been obtained from Bohemian rocks of 

 Carboniferous age ; another example of the same plant from 

 Greenland was regarded by Heer, in the third volume of the 

 "Elora fossilis Arctica," as indicative of Carboniferous rocks. It 

 was, however, shown by Krejci and Peistmantel that the coal- 



• Sternberg, Flor. Yorwelt, Heft i. p. 20. 



