Classification of Pteridophytes | Pteridophyta | Botany

All the vascular cryptogams are generally put under the Divi­sion Pteridophyta, and are divided into four classes:

Class I. Psilophytineae:

The sporophyte is leafless or pro­vided with very minute leaf-like scales; roots are also absent. The sporangia are terminal or lateral, and occur singly at the tips of the branches.

Class II. Lycopodineae:

The sporophyte is differentiated into root, stem and leaf. The leaves are microphyllous and usually spirally arranged. The branching of the stem is typically dichotomous. Leaf-gaps are absent in the vascular cylinder. The sporangia are borne singly on the adaxial face of the sporophylls and contain either homospores (e.g. Lycopodium) or heterospores (e.g. Isoetes and Selaginella). The sporophylls may or may not form a cone or strobilus. Sperms are usually biflagellate excepting in Isoetes and Stylites.

Class III. Equisetineae:

The sporophyte is differentiated into root, stem and leaf. The stem is provided with distinct nodes and internodes. The sterile leaves are usually arranged in whorls. Leaf-gaps are absent in the vascular cylinder. The sporangia are usually borne in groups on a special structure called the sporangiophore and form a distinct cone. Sperms are always multiflagellate.

Class IV. Filicineae:

The sporophyte is differentiated into root, stem and leaf. In some exceptional cases roots are entirely lacking. The leaves are macrophyllous and are arranged spirally. Morpho­logically, the sporophylls and sterile leaves are alike and they never form any cone or strobilus.

The sporangia are borne in groups forming sori, either on the margins or near about the centre on the under (abaxial) surface of the sporophylls. Leaf-gaps are present in the vascular cylinder. Sperms are always multiflagellate.

Bold (1957), however, does not accept the division Pterido­phyta, in its classical sense, and divides the vascular cryptogams into four divisions:

i. Psilophyta,

ii. Microphyllophyta,

iii. Arthrophyta and

iv. Pterophyta.

Prof. Bold’s system of classification is a negative and a retrogressive one, and it overlooks evidences of relationship and separates subdivisions of plants grouped together in other classifi­cations.

Pichi-Sermolli (1958), although agrees that the Pteridophytes are not uniform as a taxon, still he considers that these plants should stand as a ‘divisio’ in its classical sense, because they share many fundamental characters.

His division Pteridophyta includes six classes:

i. Lycopsida,

ii. Sphenopsida,

iii. Noeggerathiopsida,

iv. Psilotopsida,

v. Psilophytopsida, and

vi. Filicopsida.