A bicollateral vascular bundle is characterised by

Explanation

### Step-by-Step Text Solution:

1. **Definition of Bicollateral Vascular Bundle**: A bicollateral vascular bundle is a type of vascular bundle found in some plants, characterized by the arrangement of xylem and phloem tissues.

2. **Arrangement of Tissues**: In a bicollateral vascular bundle, the xylem is located centrally. This xylem is typically composed of larger xylem vessels.

3. **Phloem Positioning**: Surrounding the xylem, there are two layers of phloem. These layers consist of smaller cells that are organized above and below the xylem.

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