Final answer:
In whisk ferns, the xylem tissue is central and surrounded by phloem, forming a star-shaped pattern in a cross-section, which is not seen in monocots or dicots.
Step-by-step explanation:
In whisk ferns, a type of non-flowering vascular plant, the vascular tissue is organized differently compared to the more commonly studied monocots and dicots. In the stem of a whisk fern, the xylem tissue is at the center surrounded by phloem tissue. A cross-section of the xylem in whisk ferns typically appears star-shaped. This is in contrast to the arrangement found in monocots, where the vascular bundles are scattered throughout the ground tissue, and dicots, where the vascular bundles are arranged in a ring with xylem and phloem forming different patterns.
Therefore, in whisk ferns, the central cylinder of xylem surrounded by phloem, when observed in a cross-section, is star-shaped, which corresponds to answer option 'c'.