INTRODUCTION

Pteridophyta (pteron = feather, phyton = plants) are the most primitive vascular plants and are also known as ‘vascular cryptogams’. They appeared on the earth, in the mid-Paleozoic Era during the Silurian Period which began 438 million years ago. The earliest pteridophytes like Rhynia and Psilophyton were leafless and rootless plants, their sole plant body composed of green stem anchored to the soil by hair-like rhizoids which functioned like roots. The stem performed most vital functions, especially photosynthesis and transpiration. The pteridophytes diversified and evolved in their physical complexity and reproductive methods during the next 100 million years well into the Carboniferous Period, when Horsetails, Lycopods, Lepidodendrales and Psilophytales dominated the land. Many had grown into the proportions of gigantic trees that constituted the primitive Carboniferous forests, which existed before birds, and mammals and arrived and flowers bloomed on the earth. By Late Carboniferous, 300 mya, ferns with seeds (Cycadofilicales or seed ferns) had evolved. These early gymnosperms that appeared during the Carboniferous period resembled so much with the ferns that the period is often called ‘Age of Ferns’. Cordaitailes, ancestors of modern conifers and Gnetales, had also appeared around the same time. The end of Palaeozoic Era, during the Permian Period (286 mya) the tree forms of Carboniferous pteridophytes perished creating extensive coal deposits of the planet. The Mesozoic Era (248-144 mya) saw Cycads dominating the land along with other early
gymnosperms. The primitive carboniferous arborescent Lycopods and Horsetails were replaced by the ancestors of herbaceous forms.

The pteridophytes probably attained their peak of luxuriance during the carboniferous and started declining in diversity and richness thereafter. This decline continued with the so much so what is left of the pteridophytes today, apart from the fern group, are merely seven living genera: Psilotum, Tmesipteris, Equisetum, Lycopodium, Phylloglossum, Selaginella and Isoetes). The rest are extinct and represented by only by fossils. The Carboniferous had witnessed Lycopod dominated forests, some of which attained even 30 m height. Today’s coal deposits of the world are mainly from the Carboniferous Period forests. Ironically the seven genera that survive, the descendants of the Lycopods and Equisetums of the Palaeozoic, are miniatures of their past, mostly herbaceous forms to be searched amidst flowering plant dominated landscapes.