120 Scientific Proceedings, Royal Duhlin Society. 



condrusonmi, Gilkinet, from tlie Upper Devonian of Belgium. Stur's genus 

 Rhodea, from the Oulm flora, also shows some points in common with 

 A.fissilis, he finds. 



Potonie states (21) tliat in tlie Spheuophyllaoese there is a direct relation 

 between the size and degree of segmentation of the leaf and tlie age of the 

 species. The earliest known species of Sphenophyllum is S. tenerrhnuin, and 

 its leaves are formed of repeatedly forked, filiform processes. The most recent 

 Sphenoj'ihyllum — S. Tlioni — has undivided leaves, the largest of any species. 

 If Potonie's generalization were api)licable to Archfeopteris, then A. fissi/is 

 Scliml. would be the oldest species of the genus. 



In 1903 the discovery of tlie seeds of Lyginodendron oldhamium and the 

 definite establishment of the Pteridospermese,^ followed by tiie discovery of 

 seeds in Neuropteris, Pecopteris, Aneimites, &c., led to a great and sudden 

 change in the interpretation of the Palaeozoic flora. Tiie replacement of the 

 view that the leptosporaugiate ferns were the more primitive, and gave rise 

 to tlie Eusporangiatse, by the view that the Eusporangiate ferns, flourishing 

 in the PalEeozoic epoch, were tlie earlier, and subsequently gave rise to the 

 Leptosporangiatse, is now in part, replaced by the opinion that the assumed 

 Marattiaceae andOphioglossaceas of the Palaeozoic were in reality Pteridosperms, 

 and that it is only the imperfection of the geological record, or our lack of 

 knowledge of the evidence buried in the rocks, whicli prevents this view from 

 being generally demonstrated. Doubts naturally arise in the mind of one who 

 has passed through tliese various phases of a somewhat revolutionary character 

 (in keex^ing, it must be stated, with the revolutionary discoveries) as to the 

 reliability of the present view expressed by some palaeobotanists, that the 

 less highly organized spore-bearing ferns appeared later in time than the 

 seed-bearing Pteridosperms, aud that while the Pieridospii'ius are well 

 represented in the Lower Carboniferous, and possibly in the Devonian, the 

 fern-groups of to-day are unrepresented, though annulate and exannulate 

 sporangia, as well as members of the Botryopteriiieae, are met with in the 

 Lower Carboniferous. So all-embracing is the view of the eai'ly predomiuauoe 

 of the Pteridosperms, that the Upper Devonian plant, Arohseopteris, is now by 

 many palaeobotanists designated as a male Pteridosperm . 



In 1905 I arranged to make further explorations of the Kiltorcan beds in 

 Co. Kilkenny, one object being to test the validity of the view of the 

 Pteridosperm chaiacter of Archseopteiis. It is only recently that I have 

 been free to give time to examine tlie specimens of Archseopteris under my 



' 0. Hbrich, writing in Potonie's Abbild u. Beschr. d. fossil. Pflanzen (IV., p. 44 et seq., 1905) 

 thinks the evidence in favour of the establishment of the Pteridospermeije inaleqnate — a view that 

 few will share. 



