Final answer:
The peristome is a ring of toothlike structures on the upper part of the moss capsule that allows gradual spore discharge.
Step-by-step explanation:
The peristome is a ring of interlocking, toothlike structures on the upper part of the moss capsule. It is specialized for gradual spore discharge. Most moss capsules have one or two rings of teeth surrounding the opening of the capsule that can open and close, releasing spores under favorable dry conditions when they will be transported further by the wind.