Sporangia arise from the placenta or amara along the underside of the leaves of Pteris. The sporangia together form a brown kidney-shaped sorus. Each sporangium consists of two parts.
1. Pedicel or Sporangiophore: Each sporangium has a short segment at its base. It is called a stalk or sporangiophore.
2. Capsule: The upper part of sporangium is called capsule. The parts of the capsule are:
(i) Annulus: The thick covering of chitin on the capsule wall is called annulus. It is monolayer, elastic and absorbent.
(ii) Stomium: The ring in the capsule wall with a thin membrane is called stomium. It helps in spore excretion.
(iii) Spores: Inside the capsule there are sporogenous cells. 16 spore mother cells are produced from sporogenous cells. Each spore mother cell divides by meiosis to produce 4 spores. That is, 64 spores are produced from 16 spore mother cells. Spores are dark brown in color, bilayered and germpored. Spores are homosporous or homosporous.