PTERIDOPHYTA

INTRODUCTION Pteridophytes (pteron= feather, phyton= plant, i.e. plants with feather like leaves). These are also known as vascular cryptogams.

HABITAT Most of the living pteridophytes are terrestrial, growing in moist and shady places.  Some members are aquatic (Azolla, Marsilea, Salvinia) usually occurring in permanent ponds. A few forms are xerophytic like Equisetum.

HABITAT Marsilea (Aquatic) Equisetum

PLANT BODY They show much variation in their form, size and habit. They ranges from small annual (e.g. Azolla) to large tree-like perennials. The main plant body is sporophytic, differentiated into root, stem and leaves. The primary roots are ephemeral and are soon replaced by adventitious roots (which develop on rhizome). The stem is an underground rhizome by which ferns reproduce vegetatively. Some primitive ferns have tree-like stem.

PLANT BODY The leaves are scaly (Equisetum), small and sessile (e.g Lycopodium), or large, petiolate and compound (Ferns). Leaves may be small microphyllous  (Lycopodium) or large megaphyllous (Pteris). These are called fronds. The root and stem have well developed vascular system, composed of xylem and phloem. The xylem is made up of tracheid and the phloem has sieve tubes only. Cambium is absent. 

PLANT BODY

PLANT BODY

REPRODUCTION Vegetative reproduction takes place by fragmentation of rhizome, adventitious buds etc. They reproduce by spores, produced in sporangia. The sporsporangia are usually borne on the ventral surface of the leaf.  Sporangia occur on the surface of leaves in cluster called sori.(Sing. Sorus) and these leaves, bearing sporangia, are known as sporophylls The sporophylls with megasporangia are called megasporophylls and with microsporangia are called microsporophylls. Sporophylls are either unifromly distributed or are aggregated into compact cones (known as strobili) at the apex of the stem. In aquatic forms like Azolla, Salvinia, and Marsilea the sporangia are present within specialized structure called sporocarps.

SORUS

Psilopsida: Psilotum Lycopsida: Lycopodium,Selaginella Sphenopsida: Equisetum (Horse taill) Pteropsida or Filicopsida: Pteridium, Adiantum

Ornamental value : Because of their delicate and graceful foliage, ferns are grown as ornamental plants in gardens. Drugs : Rhizome and petiole of Dryopteris  yield an antihelminthic drug. Lycopodium is used in the treatment of rheumatism and Adiantum roots help to cure throat infection. Food : Some are rich source of starch. Soil binding : Pteridophytes protect the soil from erosion even along hill slopes by binding the soil. Scouring : Equisetum stems are used in scouring (cleaning of utensils) and polishing of metals. Biofertilisers : Azolla has a symbiotic association with nitrogen-fixing cyanobacterium, Anabaena. It is inoculated to paddy fields to function as a biofertilisers.