THE 



SCIENTIFIC PROCEEDINGS 



OF 



THE ROYAL DUBLIN SOCIETY, 



I. 



A SEED-BEAEING IRISH PTERIDOSPERM, CROSSOTHECA 

 HONINGEAVSI, Kidston {LYGINOBENDRON OLDHAMIUM, 

 Williamson). 



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



Professor of Botany iu the Eoyal College of Science for Ireland. 

 (Plates I.-III.) 



[Read November 22. Ordered for Publication, Decembeh 2, 1910. Published Maeoh S, 1911.] 



During the past twenty-five years the views of botanists as to the inter- 

 relationships of tlie various groups of the Vascular Cryptogams or 

 Pteridophyta, and as to their line of evolution, have profoundly changed. 

 At the beginning of tliis period it was generally thought that the ferns 

 were connected by the Leptosporangiate groups — the Hymenophyllacese (the 

 Filmy Ferns) and the Polypodiaceee with the Muscinese, through such a 

 Liverwort as Anthoceros. This view was abandoned largely as a result of 

 the researches carried out by Professor P. 0. Bower' on the embryogeuy of 

 the spore-bearing members of the Filicinese and other Pteridophyta. He 

 concluded that the earlier members of the Filicinese are the Eu-Sporaugiatse, 

 i.e. the Ophioglossacese and the Marattiaeeae. This oj^inion, based on the 

 investigation of the anatomy of living ferns, supported the evidence already 

 derived from the study of fossil ferns." The earliest and most commonly 



' F. 0. Bower: "The Origin of a Land Flora," 1908. On p. 654, the three allied families, 

 Botr3'opteride£e, Osmundaceae, and Hymeiiophyllaceas, are described as blind branches of descent. 



- Stur : " Zur Morphologie n. Sj'stemalik d. Culm u. Carbon-Farne," 1883. On p. 845 Star 

 states that the Gleicheniacefe, OsmundaceaD, and SchizseaccEe were Post- Carboniferous ; and on p. 795, 

 that the Marattiaceas reached their maximum of development (15 genera and 98 species) in the 

 Culm and Carboniferous — especially iu the Lower Carboniferous (iu M'hich the Culm of Stur is 

 now included). The rapid change of view in this branch of botanical work is indicated by E. A. N. 

 Arber (Annals of Botany, xx., p. 230), who states : — " Thus the Geological Eecord no longer supports 

 the conclusion arrived at by some botanists from a study of the recent ferns, that the Eusporangiate 

 is the more primitive type as compared witli the Leptosporangiate." Slur's many Marattiacecc are, 

 SCIENT. PEOC. E.D.S., VOL. XIII., NO. I. A 



