Published online by Cambridge University Press: 06 July 2012
The relation of the leaf-trace to the vascular system of the stem in the Ferns has been exhaustively investigated during the past fifteen years by various workers, especially by Gwynne-Vaughan and Boodle in this country and by Jeffrey and his pupils in America. The interpretations of the numerous types of Fern stele and leaf-trace have caused much discussion. And the discovery of a wonderful series of fossil Ferns has not settled the discussion of the evolution of the Filicinean vascular system, but has carried the battle on to another field.
The fossils have recently yielded up the structure of their pinna-traces (Kidston, '08; Bertrand, '09; Gordon, '11). Simultaneously an attack has been made on the pinna-traces of living Ferns. Various pinna-traces were described in curious mathematical formulæ, but no comparisons were made of the different types, by Bertrand and Cornaille ('02) in their Étude sur quelques caractéristiques de la structure des Filicinées actuelles.