1887.] Lepidodendron Harcourtii and L. fuliginosum. 



7 



have frequently had occasion to refer as " the type of L. Harcourtii" 

 characterised by the possession of a very distinct parenchymatous 

 medulla, surrounded by a sharply-defined non-exogenous vascular 

 zone — the ItJtui medullaire of Brongniart — and by the almost entire 

 absence of any exogenous vascular zone ; the chief exception to the 

 last feature being represented in the Plate 49, fig. 11, referred to 

 above. 



One of the most characteristic features seen in my new specimens 

 occurs in the structure of the foliar bundles. These have been 

 large, and in transverse sections of a stem they are rendered increas- 

 ingly conspicuous, by the disappearance of a considerable amount of 

 cellular tissue which originally belonged to them, but which is now 

 only represented by a clear vacant space. What remains of these 

 bundles is equally characteristic. In each case the bundle appears to 

 be a double one ; owing to the preservation not only of its vascular 

 or zylem part, but also of a distinct and separate string of what has 

 obviously been a modification of the hard bast of the phloem part of 

 the handle. A further feature occurs in the almost invariable disap- 

 pearance of the entire inner cortical zone. 



Visiting York a few weeks ago, I made a fresh search for Har- 

 court's original specimen, and with the kind aid of the officers of the 

 museum I was this time successful. The specimen represented on 

 Plate 98 (fig. 1), of the 'Fossil Flora,' vol. 2, was discovered, and by 

 the kindness of Mr. Reed, the intelligent Honorary Curator of the 

 geological department of this museum, I have been permitted to 

 obtain a transverse section of it. It is now certain that my more 

 recently acquired specimens represent the true L. Harcourtii, and, 

 in all probability, fig. 9 in Plate 52 of my Part XI is a very young 

 branch of the same species. Those previously figured by me and 

 referred to above are certainly distinct. They are characterised by 

 the greater uniformity in the composition of the entire cortex, the 

 inner part of which is preserved, and by the absence of the duplex 

 structure of the . foliar bundle. The small size of the cells of the 

 inner cortex, and the dense aspect both of it and of the foliar 

 bundles (see fig. 10, Plate 51, Part XI), give to transverse sections of 

 the form so sooty an aspect contrasted with the luminous semitrans- 

 parency of the true L. Harcourtii, that I propose to recognise the 

 former as Lepidodendron fuliginosum. 



