microphyll

Traditionally, a microphyll is "an appendage supplied by a single, unbranched vein".

Unusually for the lycopods, each microphyll contains a branching vascular trace.

In the classical concept of a microphyll, this vein emerges from the proto stele, without leaving a leaf gap.

Lycophytes have microphyll leaves.

The "Enation theory" of microphyll development posits that small outgrowth, or enations, developed from the side of early axes (such as those found in the Zosterophylls).

The plants are heterosporous (megaspores and microspores), and have structures called ligules, scale-like outgrowths near the base of the upper surface of each microphyll and sporophyll.

The plumbing of these leaves is interesting: the vascular traces trifurcate at the junctions, with one thread going to the microphyll, and the other two moving left and right to merge with the new branches of their neighbours.