Plant Biology and Classification

The archegonium of Selaginella is more reduced than that of Funaria, featuring an embedded venter, absence of a stalk, and a very short neck.

The neck of the archegonium in Selaginella is very short, consisting of two tiers of four cells each.

Selaginella is characterized by heterospory and the presence of ligules on its leaves.

Like all pteridophytes, the life cycle of Selaginella exhibits alternation of generations where the sporophyte is the dominant, independent, and photosynthetic phase.

The plant body of Selaginella is a sporophyte, which is diploid and produces spores through meiosis.

Selaginella is known to possess pyrenoids in its chloroplasts, which is a unique feature among many pteridophytes.

Heterosporous pteridophytes produce two types of spores (microspores and megaspores). Selaginella and Salvinia are classic examples of heterospory.

Selaginella is heterosporous, meaning it produces two types of spores. Therefore, it does not exhibit homospory.

S. rupestris is known for having uniform leaves, exhibiting homophylly, whereas most other Selaginella species are heterophyllous.

Heterospory is the production of two distinct types of spores, namely microspores and megaspores. Plants such as Selaginella and Marsilea exhibit heterospory and bear sporangia that produce these two different types of spores.

Because Selaginella has both microspores and megaspores, the plant is called as heterosporous. The other fern-allies are homosporous (having only one type/size of spore). This significance of this advance in evolution is important because sexual dimorphism is being expressed much earlier in the life cycle. The organisms to appeared next this are all heterosporous.

A resurrection plant is any poikilohydric plant that can survive extreme dehydration, even over months or years. Selaginella lepidophylla, is known as resurrection plant or birds nest moss as it shows ball like appearance (cespitose habit) in dry season. It is a plant species native to North America, Central and South America, and sold as a novelty.

Heterospory means the production of two spores of different sizes and of two different development patterns. Small spore is called microspore and large spore is called megaspore. Microspore produces the male gametophyte that possesses male sex organs while megaspore produces the female gametophyte that possesses female sex organs. It ultimately leads to seed development. For example, Selaginella, Salvinia, Azolla. Dryopteris and Adiantum are homosporous and haploid spores are produced in each sporangium. 

• Spore is uninucleate haploid spherical structure.
• The spore germinates into gametophyte known as prothallus.
• Prothallus has archegonia present on the ventral side.
• Hence, the Prothallus of Dryopteris is a Gametophyte.  It bears archegonia on the ventral side. 
• So, the correct answer is 'Gametophyte, ventral'.

In older plants, the branches bear reproductive structures at their tips. They are called as strobilus or spondiferous spike. The arrangement of micro and megasporophylls in the strobili of different species is variable. The strobili of S.oregana are among the longest in the flora and they often show several novel features. In S.kraussiana, there is only one megasporangium at the base and the rest of the sporophylls bear microsporangia.