Description of Fern Sorus - QS Study
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Fern Sorus:

Definition: The kidney shaped sporangia growing in a group on the ventral surface of a fern leaf are called fern sori.

Position: They are situated on both sides of the midrib of matured leaf from the ventral surface.

Season: Usually, sori are found to grow in the late spring or in early summer.

Colour: At the beginning, they are green, later they turn into brown colour.

Origin: On the ventral surface of the leaf, sori start growing from the special meristematic tissue or placenta.

Structure: In each sorus, numerous sporangia are present A membrane covers the sporangia called inducium

Internal structure of sporangium: Each fern sporangium comprises of two main parts

(I) Stalk &

(II) Capsule.

(I) Stalk:  It is a multicellular and slender, rod like structure growing from placenta.

a1

Fig: T.S. of fern sorus

(II) Capsule:

  • The oval shaped swollen part, situated at the tip of the stalk is called capsule.
  • Its wall is composed of a one celled layer. These cells almost cover the capsule. This cellular layer is known as annulus.
  • All the remaining cells other than annulus are thin layered which form an incomplete ring. These cells are called stomium.