name the meristems which appear later in life of dicotyledonous and gymnosperms plants and causes increase in the girth of the organ in which they are active.

Answer

**Step-by-Step Solution:**

1. **Identify the Types of Meristems:**
- In dicotyledonous and gymnosperm plants, there are two main types of meristems: primary meristems and lateral meristems.

2. **Focus on Lateral Meristems:**
- The meristems that appear later in the life of these plants are known as lateral meristems.

3. **Function of Lateral Meristems:**
- Lateral meristems are responsible for secondary growth, which leads to an increase in the girth of the plant organs.

4. **Locations of Secondary Growth:**
- Secondary growth occurs in two main areas:
- **Cork Cambium:** This is located in the outer side of the plant organ and contributes to the formation of bark.
- **Vascular Cambium:** This is located on the inner side of the plant organ and contributes to the formation of secondary xylem (wood) and secondary phloem.

5. **Conclusion:**
- Therefore, the meristems that appear later in the life of dicotyledonous and gymnosperm plants, which cause an increase in the girth of the organs, are the lateral meristems (cork cambium and vascular cambium).

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