In the ___________ the vascular cambium is completely secondary in origin:

Options

A. Monocot root
B. Monocot stem
C. Dicot root
D. Dicot stem

Answer

To solve the question "In the ___________ the vascular cambium is completely secondary in origin," we need to analyze the options provided and understand the characteristics of vascular cambium in different plant structures.

### Step-by-Step Solution:

1. **Understanding Vascular Cambium**: Vascular cambium is a type of meristematic tissue that is responsible for the secondary growth in plants. It produces secondary xylem (wood) and secondary phloem.

2. **Types of Cambium**:
- **Intrafascicular Cambium**: This is the cambium located between the xylem and phloem within a vascular bundle.
- **Interfascicular Cambium**: This is the cambium that forms between the vascular bundles.

3. **Primary vs. Secondary Origin**:
- **Primary Cambium**: This is formed during the primary growth of the plant.
- **Secondary Cambium**: This is formed from the dedifferentiation of parenchyma cells and contributes to secondary growth.

4. **Analyzing the Options**:
- **Monocot Root**: Generally lacks a vascular cambium.
- **Monocot Stem**: Also lacks a true vascular cambium and does not undergo secondary growth.
- **Dicot Root**: Contains a vascular cambium that is completely secondary in origin.
- **Dicot Stem**: Has a vascular cambium that is partially primary and partially secondary.

5. **Conclusion**: Based on the analysis, the vascular cambium that is completely secondary in origin is found in the **dicot root**.

### Final Answer:
In the **dicot root**, the vascular cambium is completely secondary in origin.

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