An example of homosporous pteridophyte is:

Question

Accepted Answer

The correct option is 1: Lycopodium

The classification of pteridophytes, commonly known as vascular cryptogams, relies significantly on the type of spores they produce. A plant is considered **homosporous** if it produces only one kind of spore, all of which are roughly the same size and morphological appearance. This single type of spore germinates to form a monoecious or bisexual gametophyte (prothallus) that bears both male sex organs (antheridia) and female sex organs (archegonia). *Lycopodium*, often called club moss, is a classic example of a homosporous pteridophyte. It belongs to the class Lycopsida and reproduces via strobili that yield spores of uniform size. This homosporous nature represents an ancestral characteristic in the evolutionary lineage of plants, contrasting sharply with the more derived state of heterospory found in the other options.

The incorrect option is 2: Selaginella

*Selaginella*, also a club moss but belonging to a different order (Selaginellales), is a textbook example of a **heterosporous** pteridophyte. The key difference in heterosporous plants is the production of two distinct types of spores: small spores called **microspores** and larger spores called **megaspores**. The microspores germinate to form a male gametophyte, and the megaspores germinate to form a female gametophyte, meaning the gametophytes are unisexual. This separation of sexes marks a significant evolutionary advancement, indicating the initial steps towards the seed habit observed in gymnosperms and angiosperms.

The incorrect option is 3: Marsilea

*Marsilea* is a well-known genus of water ferns, and it is categorically a **heterosporous** pteridophyte. It explicitly produces microspores and megaspores, which are enclosed within specialized, hard structures called sporocarps. The development of distinct male and female gametophytes from these two spore types is central to *Marsilea*'s reproductive cycle. Therefore, classifying *Marsilea* as homosporous would be incorrect, as it exhibits the advanced reproductive strategy of producing two different spore sizes with separate developmental fates.

The incorrect option is 4: Salvinia

*Salvinia*, an aquatic floating fern, is another clear example of a **heterosporous** pteridophyte, alongside *Marsilea* and *Selaginella*. This genus produces two types of sporangia, each containing either many microspores or fewer megaspores. Like other heterosporous species, the two spore types lead to the formation of distinct, reduced, and endosporic (developing within the spore wall) male and female gametophytes. In the context of pteridophyte evolution, the heterosporous condition seen in *Salvinia* is characteristic of the more advanced aquatic forms, highlighting a critical adaptation in their life cycle.