[ 177 ] 



XIII. 



FORBESIA CANGELLATA, gen. et sp. nov. 

 (SPHENOPTEEIS, sp., Baily.) 



By T. JOHNSON, D.Sc, F.L.S., 

 Professor of Botany in tlie Royal College of Science for Ireland, Dublin. 

 (Plates XIII. and XIV.) 



[Read November 28, 1911. Published January 19, 1912.] 



In the course of examination of the different specimens of Sphenopteris in 

 the Museum Collections I was struck by the three or four small slabs of 

 plant-impressions provisionally named by Baily (1) " Sphenopteris, sp.," and 

 described by him (p. 19, fig. 1) in the " Explanation of Sheets 187, 195, 

 and 196 " of the Q-eological Survey of Ireland.' The specimens were 

 obtained from the Lower Carboniferous strata, near Bandon, Co. Cork. 



Sphenopteris is not a generic name in the modern sense, but a form- 

 name introduced by Brongniart (2) in 1822 for that sterile division of 

 Schlotheim's Filicites (a term applied to Palaeozoic fossil- ferns in general) 

 which showed (1) a differentiation into stem and leaf, (2) a segmentation of 

 the leaf, with ultimate wedge-shaped lobes, or segments, and (3) a clearly 

 marked forked or pinnate venation. The venation normally consists of a 

 central or median vein running through the secondary raehis, with simple or 

 branched veinlets passing out into the pinnule segments. Baily's plant shows 

 the differentiation into axis and leaf with cuneate segments very character- 

 istically, but there is no sign in it of the venation to be found in an ordinary 

 Sphenopteris. If it was a vascular plant, it had not yet developed a definite 

 vascular system ; i.e., it was a vascular cryptogam without vascular bundles. 

 Its organisation was thus lower in type than that yet seen in any Pteridophyte, 

 living or extinct. It brings us, then, if my interpretation is right, nearer to 

 that ancestral form from which the Filicinese arose, and to this extent helps 



1 I am indebted to Professor G. A. J. Cole for the permission to examine the specimens of 

 Sphenopteris preserved in the collections of the Geological Survey of Ireland, and housed iu the 

 National Museum, Dublin. 



SOIENT. PEOC. E.D.S., VOL. XIII., NO. XIII, 2 D 



