How do sporophylls differ from ordinary leaves in lycophytes?

In lycophytes, sporophylls are specialized leaves that bear sporangia (spore cases), whereas ordinary leaves—often called microphylls—are vegetative and lack these reproductive structures.12

The differences between these leaf types vary by genus:

• General Distinction: In many lycophytes, sporophylls are aggregated into tight, conelike structures called strobili. While these sporophylls often differ in appearance from vegetative leaves, in some species they may simply occur in fertile regions along the stem and closely resemble ordinary leaves.123
• Selaginella: The sporophylls are localized in strobili and generally differ from vegetative leaves, though the degree of difference varies.43
• Isoetes: Most leaves are considered sporophylls because they bear sporangia at their expanded, concave bases. These leaves are not strictly differentiated into vegetative and reproductive types in the same manner as other lycophytes.423

Regardless of their function, both ordinary leaves and sporophylls in lycophytes are typically characterized as microphylls, meaning they possess a single, unbranched midvein.125