Comparison of Internal Structure of Leaf of Selaginella and Lycopodium

 

Comparison of Internal Structure of Leaf of Selaginella and Lycopodium

Feature	Selaginella Leaf	Lycopodium Leaf
Leaf type	Microphyllous leaf; generally small, simple, and ligulate.	Microphyllous leaf; simple and usually eligulate.
General arrangement	Leaves are commonly arranged in four rows and may be unequal in size, especially in dorsiventral species.	Leaves are usually small, simple, equal in size, and commonly arranged spirally around the stem.
Epidermis	Single-layered epidermis is present on both surfaces and is covered by a thin cuticle.	Single-layered epidermis is present on both surfaces and is covered by a cuticle.
Cuticle	Cuticle is generally thin, but it may vary according to habitat.	Cuticle is usually well developed and may be thicker in xerophytic species.
Stomata	Stomata are present, usually more common on the lower/abaxial surface.	Stomata are present, commonly on the lower surface or sometimes on both surfaces depending on species.
Ligule	A small ligule is present on the adaxial side near the base of the leaf, usually seated in a ligular pit.	Ligule is absent; this is an important distinguishing feature.
Mesophyll	Mesophyll is generally simple and chlorenchymatous, without clear palisade and spongy differentiation.	Mesophyll is also generally undifferentiated into palisade and spongy regions.
Intercellular spaces	Small intercellular spaces may be present among mesophyll cells.	Intercellular spaces may be present, but the mesophyll is usually compact.
Vascular supply	Each leaf contains a single, unbranched vascular strand or midrib.	Each leaf contains a single, unbranched vascular strand or midrib.
Vascular bundle position	The vascular bundle is placed centrally in the leaf.	The vascular bundle is placed centrally in the leaf.
Bundle sheath	The vascular strand is surrounded by a parenchymatous bundle sheath or endodermis-like layer.	The vascular strand is surrounded by a parenchymatous sheath.
Xylem position	Xylem usually lies toward the adaxial/upper side of the vascular bundle.	Xylem usually lies toward the adaxial/upper side of the vascular bundle.
Phloem position	Phloem usually lies toward the abaxial/lower side of the vascular bundle.	Phloem usually lies toward the abaxial/lower side of the vascular bundle.
Mechanical tissue	Mechanical tissue is poorly developed; some supporting cells may occur near the midrib in some species.	Supporting tissue may be present around the vascular strand, especially in firmer leaves.
Leaf trace	Leaf trace is simple and does not show branching.	Leaf trace is simple and does not show branching.
Sporophyll relation	Sporophylls are similar to foliage leaves but bear microsporangia or megasporangia; the plant is heterosporous.	Sporophylls are generally leaf-like and bear sporangia; the plant is homosporous.
Sporangium position	Sporangium develops on the adaxial side near the base of the sporophyll.	Sporangium develops on the adaxial side near the base of the sporophyll.
Special diagnostic feature	Presence of ligule and heterosporous sporophylls are key features.	Absence of ligule and homosporous sporophylls are key features.
Overall similarity	Both leaves are microphyllous and have a single unbranched vein.	Both leaves are microphyllous and have a single unbranched vein.
Main difference	Leaf is ligulate and associated with heterospory.	Leaf is eligulate and associated with homospory.

 

Key Difference: Selaginella leaf is ligulate and linked with heterospory, while Lycopodium leaf is eligulate and linked with homospory. Both have microphyllous leaves with a single unbranched vascular strand.