On the Palaeozoic pteridophylls

Abstract

The Palaeozoic pteridophylls hold an excellent intermediate osition in their entity as well as in their individual characteristics between the oldest (silurian and early devonian) plants and the land plants of today. This is also illustrated by the genera as they were named by Brogniart as ollows: Archaeopteris,Sphenopteris, Pecopteris, Neuropteris, Linopteris, Alethopteris,Callipteris. These genera demonstrate how the phylogenetic development was carried out by few elementary processes, still isolated and restrained to primitive stages. The same elementary processes also formed the structure of palaeozoic stems in their primitive stages. The mesozoic pteridophylls are a further step of phylogenetic changes towards present day leafforms.