Secondary medullary rays are produced by

Options

A. Fusiform initial
B. Interfascicular ambium
C. Phellogen
D. Ray initial

Answer

To determine what produces secondary medullary rays, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- The secondary medullary rays are associated with the vascular cambium, which consists of two types of initials: fusiform initials and ray initials.

2. **Identifying Fusiform Initials**:
- Fusiform initials are responsible for forming the axial system of secondary xylem (wood) and secondary phloem (bark). They contribute to the vertical growth of the plant.

3. **Identifying Ray Initials**:
- Ray initials, on the other hand, are responsible for producing the medullary rays. These rays are horizontal bands of parenchyma cells that connect the secondary xylem and secondary phloem.

4. **Understanding Medullary Rays**:
- Medullary rays, also known as ray parenchyma, are crucial for the radial transport of nutrients and water within the plant. They serve as pathways between the xylem and phloem.

5. **Conclusion**:
- Based on the roles of the different types of cambial initials, we conclude that secondary medullary rays are produced by the **ray initials**.

### Final Answer:
**Secondary medullary rays are produced by ray initials.**

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