The
Leaves are Microphylls and usually have one vein/leaf. A
couple of species have branched venation, however.
Cross Section of a Selaginella Leaf
The Mesophyll is
usually simple but it ranges from Uniform Lacunate (uniform means isodiametric cells & lacunate indicates prominent air
spaces) to Palisade
& Spongy. The latter is the characteristic
anatomy for dicots and is considered to be highly advanced as the Palisade & Spongy
tissues perform different functions. Homogenous Mesophyll would be ancestral or "primitive".
Cross Section of an Olive Leaf (Dicot)
Most species have typical chloroplasts, but one species has large cup-shaped chloroplasts. This could be
an interesting research project for someone interested in plastid evolution.
Stomata
are present. The lack of stomata on the stem
indicates that the Leaves are the primary sites of Carbon Fixation. This is a further step
in the specialization of the aerial system with regards to the primary locus of
photosynthesis.
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