Botany and Plant Science

Selaginella rupestris or rock spike moss belongs to the family Selaginellaceae. The plant is heterosporous with the presence of both megaspores and microspores. However, the variation in sporangial distribution pattern in the strobili is related to the number of megaspores per megasporangium. More than often, the megasporangiate has only 1  megaspore per megasporangium.

• The sporangia produce spores by meiosis in spore mother cells. The spores germinate to give rise to inconspicuous, small but multicellular. free-living, mostly photosynthetic thalloid gametophytes called prothallus.
•  These gametophytes bear male and female sex organs called antheridia and archegonia, respectively. 
• The microspore germinates to form the male gametophyte. 
• The first unequal division (1-1) in a microspore results in the formation of a small lenticular prothallial cell (vegetative cell) and a large antheridial initial. The prothallial cell does not divide further. 
• Hence, prothallial cells in the male gametophyte of Selaginella is 1.
• So, the correct answer is '1'.
  

Pteridophytes are vascular plants. Leaves called sporophylls produce clusters of capsular structures called sporangia that bears spores which germinate and yield gametophytes. Hence they show alternation of generations, in which a sporophyte produces spores through meiosis and a gametophyte forms gametes by mitosis. 

Option D is mismatched as the sporangia in selaginella contain four very large yellow spores. These four are the result of meiosis from a single sporocyte. The spores are called megaspores because of their large size. This makes the sporangium a megasporangium and the sporophyll a megasporophyll.

Rhizophores is a  structure of controversial morphological nature.They are leafless and  positively geotropic organs that have localised origin and develop from angle meristems. Goebel and Bower considered them as Organs sui generis (i.e.,neither roots or shoots). According to J.C.Shoute,Organ sui generis is one that is a novelty and has not arisen as result of  metamorphosis of any organ.

In Dryopteris sori, a group of sporangia covered with indusium are present along the margin of pinnae or leaflets. In it 2-8 sori are borne on the abaxial surface of the mature fronds (sporophylls). They are situated in two rows at the tips of the veinlets in between the midrib and the margins. The sori appear reniform due to the kidney shaped protective thin and membranous covering, called as indusium.

In Pteridophyte Dryopteris the gametophytes give rise to sporophyte by gametic union and sporophyte gives rise to gametophyte by forming haploid spores after meiosis. 

Young sporophyte of Pteris draws nourishment from the foot. Foot is formed first, which absorbs water, minerals from prothallus. Prothallium, or prothallus is usually the gametophyte stage in the life of a fern or other pteridophyte. The prothallium develops from a germinating spore. It is a short-lived and inconspicuous heart-shaped structure typically 2-5 millimeters wide, with a number of rhizoids (root-like hairs) growing underneath, and the sex organs: archegonium (female) and antheridium (male). Appearance varies quite a lot between species. Some are green and conduct photosynthesis, while others are colorless and nourish themselves underground as saprotrophs. 

Dryopteris species can be identified by the circular shaped sori, that is covered by a kidney-shaped, translucent tissue. It is called as indusium. It is a shield like outgrowth of the leaves.

Some epidermal cells give rise uniseriate bicellular brown hairs on young leaves of Pteris or any other fern, called as ramenta. 

In the male gametophyte of Selaginella, the single prothallial cell is the only vegetative structure, as the rest of the cells develop into the antheridium.

Dryopteris, is a genus with more than 250 species and is widespread in the temperate zones in northern hemisphere. The diploid sporophyte and haploid gametophyte of Dryopteris regularly alternate with each other. The haploid spore which gives rise to the gametophyte which is the monoecious prothallus and bears sex organs on its ventral side. After fertilization, they give rise to the sporophyte which is the dominant asexual member in the life cycle of the plant and is a perennial evergreen, differentiated into rhizome (stem), roots and leaves. Hence, both the gametophyte and sporophyte are independent of each other.

Dorstenia is a genus in the Moraceae family known for its unique inflorescence called a coenanthium, where the receptacle is fleshy and concave.

Microspores of Selaginella are very small, typically measuring around 15 micrometers in diameter.

In Dryopteris the opening mechanism of sporangium is effectively operated by stomium. Stomium is formed of the thin-walled cells, marking the line or region of dehiscence of a fern sporangium. It is the opening in an anther, usually between lip cells through which dehiscence occurs.