Classification of Pteridophytes - Practice Questions & MCQ

Pteridophyta is classified into four classes called as

1. Psilopsida (Psilotum),
2. Lycopsida (Selaginella, Lycopodium),
3. Sphenopsida (Equisetum) and
4. Pteropsida (Dryopteris, Pteris, Adiantum etc. commonly called as Ferns).

Psilopsida:

• These are the oldest known land inhabiting plants
• They are rootless, however, rhizoids are present.
• These species are homosporous i.e. they produce only one kind of spores. Homosporous.
• Most of them are present as fossils. 
• E.g. Psilotum

Lycopsida: 

• These are also called Club mosses or spike mosses.
• In the members of Lycopsida, roots, stems and leaves are present.
• These are microphyllous species i.e. they possess smaller leaves
• Lycopsids can be homosporous or heterosporous.
• Eg  Lycopodium, Selaginella.

 Sphenopsida: 

• At nodes, whorls of small leaves are present.
• Silica deposition in stems.
• Ridges and grooves in stems.
• Sphenopsids are Always homosporous
• Eg Equisetum

Pteropsida:
 

• The stem is Rhizome
• The large leaves are aerial and pinnately compound and called as Fronds. 
• The young leaves are coiled around themselves like watch spring (Circinate vernation) and petioles are covered by brown hairs called Ramenta.
• The leaflets show open dichotomous or furcate venation. 
• Sori of sporophyll is covered by a membranous sheath called Indusium. 
• In Pteris, the reflexed margin of the leaflet of sporophyll that protects the sorus is called as false Indusium. 
• Eg. Dryopteris, Pteris, Adiantum.

 Economic importance of pteridophytes:

• The pteridophytes are a good source of food for animals. The sporocarps of Marsilea are used for starch which is cooked and eaten.
• Pteridophytes can bind soil strongly, thus helping in protection from soil erosion.
• Equisetum also called scouring rushes are used to clean and polish metals.
• Azolla, a fern helps in nitrogen fixation by associating with Cyanobacteria.
• Pteridophytes are used as ornamental plants also.