In Pistia, vegetative propagation takes place by:

Options

A. runner
B. sucker
C. offset
D. stolon

Explanation

**Step-by-Step Solution:**

1. **Understanding Vegetative Propagation:**
- Vegetative propagation is a form of asexual reproduction in plants where new individuals are produced from the vegetative parts of the parent plant without the formation of seeds.

2. **Identifying the Plant in Question:**
- The plant in question is Pistia, which is commonly known as water lettuce.

3. **Exploring the Options:**
- The options provided for the mode of vegetative propagation in Pistia are:
- a) Runner
- b) Sucker
- c) Offset
- d) Stolon

4. **Analyzing Each Option:**
- **Runner:** This is a type of vegetative structure found in plants like strawberries. It allows for the plant to spread horizontally. Therefore, this option is incorrect for Pistia.
- **Sucker:** This is a vegetative structure found in plants like bananas, where new shoots grow from the base of the parent plant. Thus, this option is also incorrect for Pistia.
- **Offset:** This structure is associated with plants like the water hyacinth (Eichhornia) and is not the correct term for Pistia. Hence, this option is incorrect as well.
- **Stolon:** This is a horizontal stem that grows along the ground and can produce new plants at its nodes. In Pistia, vegetative propagation occurs through stolons, which produce daughter plants that can detach and float away to form new colonies.

5. **Conclusion:**
- Based on the analysis, the correct answer for how vegetative propagation occurs in Pistia is **stolon**.

**Final Answer:**
- In Pistia, vegetative propagation takes place by **stolon**.

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