In fern, archegonia occur on

Options

A. Leaves
B. Roots
C. Prothallus
D. Sporophyte.

Answer

### Step-by-Step Solution:

1. **Understand the Question**: The question asks where archegonia, the female reproductive structures, occur in ferns.

2. **Identify the Structure of Ferns**: Ferns are classified as pteridophytes, which are seedless vascular plants. They have a complex life cycle involving two distinct stages: the sporophyte and the gametophyte.

3. **Sporophyte and Gametophyte**: In ferns, the sporophyte is the dominant stage, which is the leafy plant we typically recognize as a fern. The gametophyte stage is represented by a small, heart-shaped structure called the prothallus.

4. **Location of Archegonia**: The archegonia, which are the female sex organs, are located on the prothallus. The prothallus is a free-living, photosynthetic structure that arises from the germination of spores.

5. **Conclusion**: Based on the information, we can conclude that archegonia occur on the prothallus of ferns. Therefore, the correct answer to the question is option 3: prothallus.

### Final Answer:
In ferns, archegonia occur on the **prothallus**.

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