Fern prothallus is a companion plant. That is, male genitalia and female genitalia are produced in the same thallus. Its reproductive process is described.
(i) Spermatogenesis: Inside the antheridium there are 20-50 sperm mother cells or androcytes. Each spermatozoon matures into a multi-flagellated spermatozoon. Spermatozoa break through the cap cells at the top of the antheridium and come out.
(ii) Ovulation: Inside the archegonium there are a few cervical duct cells, a ventral duct cell and a large ovule cell. The ovum develops into an ovum.
(iii) Fertilization: The ducts of mature archegonium are filled with mucilage and malic acid. The sperm reach the archegonium with the help of rain water or dew drops. Archegonium’s malic acid attracts sperm. Sperm and egg unite. Fertilization results in the formation of a zygote.
(iv) Germination: Zygote is enveloped by wall and becomes spore. The spore germinates in a favorable environment and divides repeatedly in the process of mitosis to form a new sporophyte.