The peristome is a specialized structure found in the capsules of mosses. It plays a crucial role in the dispersal of spores, which is an essential process for the reproduction of mosses. The correct answer to the question is option 'C' - spore dispersal.

**Function of the Peristome in Moss**

The peristome is a ring of teeth-like structures located at the opening of the capsule in mosses. It is derived from the remnants of the sporophyte's opercular ring. The peristome teeth are typically hygroscopic, meaning they respond to changes in humidity and moisture levels.

**Mechanism of Spore Dispersal**

The peristome teeth in mosses have two layers - the exostome and the endostome. The exostome is the outer layer and consists of thickened, tooth-like structures that are hygroscopic. The endostome is the inner layer, made up of delicate membranes or perforated plates.

When the humidity is high, the peristome teeth absorb moisture from the surrounding environment, causing them to curve outward and open up. This allows the spores within the capsule to be exposed to the outside environment.

As the humidity decreases, the peristome teeth lose moisture, causing them to curve inward and close. This closing action helps prevent the spores from being released prematurely.

**Role in Spore Dispersal**

When the peristome teeth are open, they create small openings or gaps between them. These gaps act as narrow slits or pores through which the spores are gradually released. The teeth also function as barriers, preventing the spores from being released all at once.

The movement of the peristome teeth in response to humidity changes helps regulate the gradual release of spores, ensuring their dispersal over an extended period. This mechanism increases the chances of spores being carried away by wind currents, water, or other agents to suitable locations for germination and establishment of new moss colonies.

In conclusion, the function of the peristome in moss is spore dispersal. The hygroscopic nature of the peristome teeth allows them to respond to changes in humidity, gradually releasing spores through small openings. This mechanism increases the efficiency of spore dispersal and contributes to the reproductive success of mosses.