Brief notes on the Types of mature sporogonium

The mature sporogonium is differentiated into foot, seta and capsule.

Foot

The foot is comparatively small, conical structure and forms the basal portion of the sporogonium. It lies embedded in the tissues of gametophyte and absorbs water and nutrients for the sporogonium.

Seta

It is more than an inch length, slender stalk bearing a capsule at its tip. It helps in conduction of food and water and also elevates the capsule for the better dispersal of spores.

Capsule

The capsule is a pear-shaped structure containing spores present at the tip of seta. The young capsule is erect and green but at maturity it turns yellow and becomes pendant.

The capsule can be divided into three distinct regions – apophasis, theca (the fertile region), and operculum arranged from the base to apex. A longitudinal section of the capsule reveals the following structures.

(i) Apophysis (Plural – apophyses)

It is expanded basal sterile part of the capsule which is the direct continuation of seta. It bears stomata. It supplies nutrition to the fertile part of the capsule.

(ii) Theca

The theca is the enlarged middle fertile part of the capsule. The jacket of the capsule is multilayered, composed of colorless parenchyma cells.

The outermost H is compact and forms the epidermis. Internal to the epidermis, there is a mass of spongy parenchyma cells containing abundant chloroplasts. This tissue constitutes the photosynthetic tissue. Internal to this spongy parenchyma tissue and external to spore sac, there is a large cylindrical cavity, traversed by delicate strands of elongated green parenchyma cells, known as trabeculae.

The central part of the capsule consists of a mass of thin walled, sterile parenchyma known as columella. The columella is surrounded by a narrow spore sac, bounded externally by 2-3 layers of cells. The spore sac contains numerous spore mother cells (2n) from which spores (n) are formed by meiosis. The haploid spores form the beginning of gametophytic generation.

(iii) Operculum

The uppermost lid or cap-like conical part of capsule is operculum. The base of the lid is surrounded by a ring of large cuticularised epidermal cells known as annulus. The innermost layer of operculum contains a double row of superposed, teeth like structure known as peristome.