How did microphylls evolve from early plant structures?

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club moss — lycophyte Club moss (*Lycopodium annotinum*).

Microphylls evolved from simple, multicellular tissue outgrowths known as enations that appeared along the aboveground axes of early Devonian Period plants. These enations served to increase the surface area of photosynthetic tissue available for light capture.1

Over time, these structures developed into the microphylls characteristic of the Lycopsida, which are defined by having a single, unbranched vein. This evolutionary development allowed lycophytes to become the first plants to possess well-differentiated shoot systems consisting of branching stems and leaves. Unlike the complex megaphylls found in other plant groups—which evolved through the webbing of branching stem systems—the simplicity of the microphyll means its vascular connection to the stem does not create a leaf gap.213