What is circinate vernation in fern leaves?

Circinate vernation is the characteristic manner in which fern leaves, or fronds, expand from the bud. Instead of unfolding from a folded condition like the leaves of many other plants, a fern leaf unrolls from the tip.12

During this process, the developing leaf takes on the appearance of a coiled spiral known as a fiddlehead or crosier. This coiled structure serves a protective function, shielding the delicate embryonic cells at the tip of the growing leaf with scales or hairs as it matures. As the leaf grows, it typically follows an acropetal pattern, meaning the tissues mature from the base toward the tip, where the youngest tissues are located.123