Question

Name the four classes of Pteridophyta with one example?

Answer 1

Hint: The phylum Pteridophyta consists of the first terrestrial plants to have a vascular system in them. It consists of horsetails and ferns which are mostly used for medicinal purposes or as ornamentals. The dominant phase in the life cycle of pteridophytes is diploid (sporophytic plant body).

Complete Answer:
The four classes of Pteridophyta are as follows:
Psilopsida: These are considered as the most primitive forms of pteridophytes as they do not have any roots, instead root- like structures known as rhizoids are present.
- Spores produced by them are of the same shape and size i.e. homospory.
- The gametophytes of such plants are non- green, cylindrical- shaped, and grow as saprophytes on a fungus.
- An example of Psilopsida includes Psilotum.
Lycopsida: The sporophytic body of plants belonging to Lycopsida is divided into well- defined root, stem, and leaves.
- Their leaves are of small size and thus known as microphylls.
- Sporangia are borne on the upper (adaxial) side of the sporophylls.
- The spores produced may be the same such as in Lycopodium or of two types as seen in Selaginella.
- Selaginella bryopteris is an example of Lycopsida.
Sphenopsida: The plants of this class are referred to as horsetails as their appearance is similar to that of the tail of a horse.
- Their leaves are extremely diminished and instead are present in the form of whorls from nodes.
- Sporangia are borne on a stalk called sporangiophore.
- Most of the plants of Sphenopsida are homosporous in nature.
- Equisetum is an example of Sphenopsida.
Pteropsida: The plants of this class are some under ferns. Ferns have large leaves and thus are known as macrophylla.
- These plants are perennial i.e. remain green throughout the year.
- Dryopteris, Pteris, and Adiantum are examples of Pteropsida.

Note:
- Selaginella has a special structure present in it known as rhizophore which is neither root or stem.
- Selaginella has medicinal properties and is known as Sanjeevni booti.
- The precursor of seed habit was first seen in the heterosporous plants of Pteridophyta.