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leaf gap[′lēf ‚gap]
(also lacuna), a break in the central cylinder, or stele, of a plant stem where the vascular bundles branch off into the leaf. It is formed over the leaf trace that extends from the stele. Leaf gaps are particularly noticeable in the stems of plants in which the conducting system of internodes forms a continuous cylinder. The larger the leaves, the wider the leaf gap. The leaf gap is particularly large in ferns. If a leaf has several traces, they generally enter the stem separately (trilacunar and multilacunar nodes). Less commonly, the traces come together to form a single leaf gap.