Modifications of Cortical Cell Walls in Roots of Seedless Vascular Plants

Forty‐three species of seedless vascular plants were assessed for modifications to root cortical cell walls. All species except Lycopodium had an endodermis with distinct Casparian bands. Experiments with the apoplastic tracer berberine hemisulfate showed that walls of all root cortical cells in the two Lycopodium species tested were permeable to this tracer. Although most species examined lacked a hypodermis several Equisetum species had a hypodermis with modified walls. Three Selaginella species had distinct Casparian bands in this cortical cell layer. This layer, therefore, is an exodermis in Selaginella and its presence limited the inward diffusion of the apoplastic tracer berberine hemisulfate.