AN EXTINCT PLANT OF DOUBTFUL 



AFFINITY. 



IN two previous articles l some account has been given of 

 the genus Sphenophyllum, with special reference to the 

 structure of the strobilus. I now propose to add a brief 

 summary of our knowledge of this interesting type of 

 extinct plants, which has been fully dealt with by William- 

 son and Scott in their memoir on Catamites, Calamostachys, 

 and Sphenophyllum} 



Every collector of Coal-Measure plants must be 

 familiar with the fragments of slender stems bearing 

 regular whorls of wedge-shaped leaves, which are fre- 

 quently found in the Upper Carboniferous shales, or in the 

 ironstone nodules of Coalbrookdale and other places. 

 Writing in 1822, Brongniart 3 describes and figures a 

 well-preserved impression of a species of Sphenophyllum 

 under the name Sphenophyllitcs cmarginatus, and speaks 

 of it as a plant without any living generic analogue. In 

 the classic Prodrome dune histoire des vegUazix fossiles, the 

 same author eives the following definition of this fossil 

 genus, and adopts the generic name Sphenophyllum i : — 



" Tige simple, articulee ; feuilles verticillees, au nombre 

 de six a douze, distinctes jusqua leur base, cuneiformes, 

 entieres ou emarginees, ou meme bifides, a lobes plus ou 

 moins profondement lacinies, presque dichotomes. Fructi- 

 fication inconnue." It is unnecessary to give any historical 

 sketch of the various opinions expressed by later writers on 

 the nature of this characteristic plant, but we may at least 

 point out, that it has been held by certain authors that the 

 plant regarded by Brongniart and others as an autonomous 

 genus, was in all probability a particular form of calamitean 

 branch. Stur was one of those who held this view, and in 



1 f ' Science Progress," vol. i., p. 54, and vol. i\\, p. 261. 



2 Williamson and Scott. 3 Broni:r.iart (1). PI. xiii., fig. 8. 

 4 Brongniart (2), p. 6S. 



