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Classification of pteridophytes

Pteridophytes are classified into four classes: Psilopsida, Lycopsida, Sphenopsida, and Pteropsida. Psilopsida includes the oldest vascular plants with scale-like leaves and spores produced directly on the stem. Lycopsida have well-defined roots, stems, and microphyllous leaves. Spores are borne in strobili. Sphenopsida only contains the living genus Equisetum, with nodes, whorls of small leaves, and sporangiophores bearing spores. Pteropsida contains most ferns, with large megaphyllous fronds, rhizomes, and sori of sporangia

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Classification of Pteridophytes Sankrita Gaonkar Assistant Professor in Botany sankrita002@gmail.com
Contents • Classification of Pteridophytes • References
Classification of Pteridophytes Pteridophytes were classified by Oswald and Tippo in 1942 into following four classes: 1.Psilopsida 2.Lycopsida 3.Sphenopsida 4.Pteropsida
Psilophyta • Most of the species are now fossils. This group includes some of the oldest vascular plants. • Plant body does not have roots. The rhizome is subterranean and it has an aerial shoot. • The stem has dichotomous branches. • There are small rhizoids coming out of rhizome. These help in absorption of water and salts. • On the shoot the leaves are either scale like arranged in a spiral as in Psilotum or leaf like appendages as is Tmesipteris. • There is no secondary growth in the stem. • The sporophyte is homosporous as the spores are similar. • The sporangia are present either at the tip or laterally directly on the stem; i.e they are cauline in position. • The antherozoids are flagellated and spirally coiled.
Psilotum Tmesipteris
Lycopsida • The plant body is differentiated into well-defined root, stem and leaves. • The leaves are small that is they are microphyllous. • The branching is dichotomous. • The sporangia are present in the axil of sporophylls. • The sporophylls are arranged as strobili. • The sporophyte is either homosporous as in Lycopodium or heterosporous as in Selaginella. • The gametophyte develops independently.
Lycopodium Selaginella
Sphenopsida • This class has only one living genus called Equisetum. • The stems have distinct nodes and internodes. • Branches are arranged in whorls. • Very small leaves are arranged in whorls at the nodes of stems and branches. • There is a special appendage called sporangiophore in which the sporangia are formed. • Equisetum is homosporous. • The gametophyte is photosynthetic. • There are multiple flagella present on antherozoids.
Equisetum
Pteropsida • Most prominent members of this class are ferns. • There are more than 9000 species in this group and is the largest group of pteridophytes. • These plants are highly evolved than other pteridophytes. • Members of this class are found in all kinds of habitat; terrestrial, damp and shady places, even in water and some are epiphytes too. • The plant body is differentiated into well-defined root, stem and leaves. The leaves are arranged spirally. • The rhizome is thick and short. • The leaves are large in size (megaphylls). They are pinnately compound and are called frond. • Young fronds are coiled. • Except for aquatic ferns others are all homosporous. • Sporangia are located at the margins and tip of leaves on the ventral side of leaves. These are present in clusters called sori.
Adiantum Marsilea Salvinia Pteris
References • Vashishta BR. 2010. Botany for degree students: Pteridophytes. S. Chand & company ltd. • Pandey B.P. (2009). Botany for degree students: B.Sc. First Year. S. Chand & Company Ltd. New Delhi.