The leaflets of compound leaves also display Circinate Vernation. However, size is not the chief characteristic of Megaphylls. A megaphyll is a leaf which contains more than one vein and its leaf trace is associated with a leaf gap in the stele . A leaf gap occurs when the departure of a leaf trace from the stele results in the development of parenchyma rather than vascular tissues in the stele, just above the leaf trace. This gives the stele a dissected appearance like the Dictyostele on the right.
Some ferns have very simple leaf organization with little mesophyll differentiation.
Others have a complex anatomy which rivals the structural specialization of angiosperm leaves. The concept of a leaf gap is a little challenging because you need to think in three dimensions. I am including some drawings by Salvador Webi who is my favorite surrealist artist. A Leaf Gap is present when a Leaf Trace diverges from the stele without its immediate replacement by vascular tissue. I have tried to illustrate this below.