In which type of vascular bundle, xylem is covered on both side by phloem?

Options

A. Radial
B. Conjoint
C. collateral
D. bicollateral

Answer

To solve the question, "In which type of vascular bundle, xylem is covered on both sides by phloem?", we will analyze the options provided.

### Step-by-step Solution:

1. **Understanding Vascular Bundles**:
- Vascular bundles are arrangements of xylem and phloem tissues in plants that facilitate the transport of water, nutrients, and food.

2. **Analyzing the Options**:
- **Radial Vascular Bundles**: In this type, xylem and phloem are situated on different radii. For example, xylem might be on one side and phloem on another, but not surrounding the xylem.
- **Conclusion**: This option is incorrect.

- **Conjoined Vascular Bundles**: This term typically refers to bundles where xylem and phloem are found together, but not necessarily surrounding one another.
- **Conclusion**: This option is also incorrect.

- **Collateral Vascular Bundles**: In collateral bundles, xylem and phloem are located on the same radius, with phloem positioned on the outer side of the xylem.
- **Conclusion**: This option does not fit the requirement since phloem is not on both sides of xylem.

- **Bicollateral Vascular Bundles**: In bicollateral bundles, xylem is surrounded by phloem on both sides. This means that there is phloem both outside and inside the xylem.
- **Conclusion**: This is the correct option.

3. **Final Answer**: The type of vascular bundle where xylem is covered on both sides by phloem is **bicollateral**.