XVI International Botanical Congess

Current knowledge reveals a substantial difference in architecture and anatomy between the primitive trimerophyte-derived plants of the Early Devonian and the more advanced forms of the Late Devonian and Early Carboniferous, amongst which living groups are recognised. Yet very little is known about how these later plant groups evolved from the earlier ones, although the transitional types must surely be represented amongst the Middle Devonian floras. As an example, some of the pitfalls of trying to establish the origins of 'ferns' are explored. New data on important Middle Devonian plant groups (Cladoxylopsida, Iridopteridales), including both anatomical and morphological details, suggest improved whole-plant concepts which might be expected to help to resolve important issues concerning phylogeny of early 'fern-like' plants. Even so the small number of useful characters and rampant parallelism remain the main hindrances to convincing cladistic analysis. Alternative means of analysis could prove more successful.