In .......... tracheids, thickening material is deposited in the form of rings.

Answer

**Step-by-Step Solution:**

1. **Understanding Tracheids**: Tracheids are elongated cells in the xylem of vascular plants that facilitate the conduction of water and minerals. They also provide structural support.

2. **Types of Thickening Patterns**: The thickening of the cell walls in tracheids can occur in various patterns, including:
- Annular (ring-like)
- Spiral
- Scalariform (ladder-like)
- Reticulate (net-like)
- Pitted

3. **Identifying the Correct Pattern**: The question asks specifically about the type of tracheids where the thickening material is deposited in the form of rings. Among the types listed, the annular thickening is characterized by rings.

4. **Conclusion**: Therefore, the answer to the question is that in **annular tracheids**, the thickening material is deposited in the form of rings.

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