Psilopsida is a group of ferns under the division Tracheophyta. They are commonly known as whisk ferns. It has two orders under it – Psilophytales and Psilotales. In the early nomenclature of IUCN, Psilopsida was included under Pteridophytes, but later Latter Eames did further study and realised that the vascular system of Psilopsida is very different from Pteridophytes and therefore named a new division Tracheophyta.
Tracheophyta has four subdivisions which are as follows:
Characteristics of Psilopsida
- Seedless plants
- They are rootless plants, rhizomes exist as underground stems where the sporophyte is anchored.
- The shoots grow aerially and branch into smaller stems.
- Rhizomes have hair-like structures called rhizoids which are responsible for the absorption of water and nutrients.
- The vascular system is very simple, primitive and protostelic.
- The plant is usually leafless and leaves if present are in the appearance of scaly appendages or foliage leaves.
- The plant grows as a sporophyte.
- Secondary growth is not present.
Life Cycle of Psilopsida
- Sporangia are found on the aerial leaf-like appendages which bear spores.
- The spores are formed meiotically in groups of four from the spore mother cell.
- The spores are released from the plant and find wet soil to germinate.
- The spores give rise to a gametophyte which is very tiny and colourless.
- The gametophyte bears archegonia and antheridia.
- The fertilisation of the egg and sperm takes place via water.
- The resulting zygote then develops into a new sporophytic body.
Also read: Pteridophytes
Psilopsida is a group, which is under constant renaming and regrouping.
Explore BYJU’S Biology to learn more about plants and their characteristics.
Frequently Asked Questions
Give two examples of Psilopsida
Psilotum and Tmesipteris are two living examples of Psilopsida.
Is Psilopsida extinct?
Only two living species Psilotum and Tmesipteris are known. All the others have gone extinct.
How does Psilopsida reproduce?
Psilopsida are known to reproduce sexually with the help of spores, which are formed in the sporangia.