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 need to understand the different types of vascular bundles and how xylem and phloem are arranged within them.

### Step-by-Step Solution:

1. **Understanding Vascular Bundles**: Vascular bundles are made up of conducting tissues, which include xylem (responsible for transporting water and minerals) and phloem (responsible for transporting food).

2. **Types of Vascular Bundles**: There are several types of vascular bundles based on the arrangement of xylem and phloem:
- **Amphicribal**: In this type, phloem surrounds xylem concentrically. This means that phloem is on the outside of xylem, but not on both sides.
- **Radial**: In radial vascular bundles, xylem and phloem are located on different radii. They are not surrounding each other.
- **Bicollateral**: In bicollateral vascular bundles, xylem is present in the center, and phloem surrounds it on both sides. This means that there is phloem on the outer side of xylem and also on the inner side.
- **Collateral**: In collateral vascular bundles, xylem and phloem are present on the same radius, with phloem located only on the outer side of xylem.

3. **Identifying the Correct Type**: The question specifically asks for the type of vascular bundle where xylem is covered on both sides by phloem. From our analysis, this arrangement is found in the **bicollateral** type of vascular bundle.

4. **Conclusion**: Therefore, the correct answer to the question is **bicollateral**.

### Final Answer:
**Bicollateral**