Classification of Pteridophytes
Pteridophytes are the "spore bearing vascular plants" and belong to the cryptogams. They were first recognised in the Silurian period of the late paleozoic age and have been divided into four main groups: Psilopsida, Lycopsida, Sphenopsida and Pteropsida.
Modern botanists have dropped the term Tracheophyta as taxon, raising the different groups of lower vascular plants themselves to division level. Smith (1955) divided the vascular cryptogams into four divisions.
Pteridophytes constitute a significant and important group in the plant kingdoms as the first true land plants. Pteridophytes are the "spore bearing vascular plants" and also called as seedless vascular plants belong to the cryptogams.
The term Pteridophytes is derived from two words "Pteron meaning feather" and "phyton meaning plant". Thus Pteridophytes are the plants with feather like leaves. Their first traces were recognised in the Silurian period of the late paleozoic age. Pteridophytes occupy a transitional position between bryophytes and spermatophytes.
Since a long time vascular plants are usually divided into pteridophyta and spermatophyta. This classification was based on the assumption that the former lack the seeds while for the latter produced them. But the discovery of pteridophytes (seed bearing ferns) broke down this artificial classification.
In 1935, Sinnott introduced term Tracheophyta to include all vascular plants. Tracheophyta are further divided into four main groups : Psilopsida, Lycopsida, Sphenopsida and Pteropsida. But it is not certain whether these are divisions or classes.
In 1953, Haupt considers them as classes in the division Tracheophyta. While many other like Zimmermann (1930), Arnold (1947), Wardlaw (1952), regard them as divisions.
Arthur J. Eames (1936) classified Tracheophyta into four groups on the basis of nature and relation of leaf and stem vascular anatomy and position of sporangia :-
Tippo (1942) called the 'groups' of Eames as sub-phylum. Wardlaw (1955) gave them the rank of sub-division.
A good number of botanists (Eames,1936; Darrah, 1939; Campbell,1940; Arnold, 1949) treat Pteridophyta as a single unit ( a division of plant kingdom) with four major groups (subdivisions)
According to recommendation of I.C.B.N (1952), the name of the division should end in the suffix-phyta, and the subdivision should end in the - opsida.
On this basis, Wardlaw (1955) divided the Pteridophytes into four divisions :
